3. Agricultural Land-Use

3.1 Introduction

The beginning of agriculture dates back to a period in human history almost ten to twelve thousand years ago. At this time, humans in several different regions of the world began domesticating several wild species of plants and animals. Some of the first crops to be domesticated were the ancestors of today's modern grains. By continuously replanting only the largest and healthiest of these plants over the centuries, these once wild plants were selectively adapted to local growing conditions. As a result of this selective breeding, present day strains of rice, wheat, and other grains are far more productive than their acient relatives.

Table 3.1: Original source region for various modern crops grown in abundance today.

The rise of agriculture also brought about cultural and societial changes to the early human population. In hunter gatherer societies nearly everyone was involved in the collection of food. However, early agriculture required a smaller proportion of human society to produce food for the rest, allowing the people not involved in farming to pursue other cultural endeavors. Early agriculture also allowed once nomadic people to established themselves in one location.

Early agriculture was primarily subsistence in nature. Farmers generally only grew enough food to feed the themselves and their extended families. The invention of the plow approximately 7000 years ago changed this practice. With the development of the plow, food supplies and human population sizes could increase by simply cultivating more land. As a result of the greater food supplied and increased population growth,human communities began organizing in villages, towns, cities, and nation states. While the devlopment of the plow had a positive influence on the development of humankind, its influence on nature and the environment was generally negative. Massive land clearing, for the purpose of growing more food, destroyed and degraded the habitats of many types of wildlife.

In the 19th and 20th centuries, humankind realized that the growing human population was running short of new sources of land for cultivation. A new technology had to be developed to expand food resources without requiring more land for cultivation. Since 1950, sharp increases in agricultural productivity have come from what is commonly called the green revolution. The green revolution increased yields by planting monocultures of hybrid crop varieties and by the application of large amounts of inorganic fertilizer, irrigation water, and pesticides. Between 1950-1970, this approach resulted in dramatic increases in crop yields mainly in more developed countries(MDCs ). After 1967, a variant of this 1st green revolution was transmitted to many less developed countries(LDCs) through MDC sponsored development projects. This 2nd green revolution involved the cultivation of new high yield, fast-growing dwarf varieties of rice and wheat, specially bred for tropical and subtropical climates. However, achieving high yields with these new crops still required large inputs of fertilizers, water and pesticides. For many LDCs, these inputs are impractical because of their high cost.

Increasing agricultural productivity through green revolution technologies relies heavily on the use of fossil fuels for running machinery and producing fertilizers. Today, it now takes about 1.2 barrels of oil to produce a single ton of grain in more developed countries. This is some seven times greater than from 1950. Thus, industrial agriculture has become addicted to oil, using about 8 % of world oil output. Many LDCs do not have the finances to buy the oil needed to run an industrialized agricultural system.

Future increases in production are predicted to come from genetic engineering and other forms of biotechnology. In the next 20 to 40 years, scientists hope to breed high yield plant strains that have greater resistance to insects and disease, thrive on less fertilizer, make their own nitrogen fertilizer like legumes, do well in slightly salty soils, and make more efficient use of solar energy during photosynthesis. A good example of the products that can be created from this type of research is triticale. Triticale is a new cereal grain produced by cross breeding wheat and rye. Triticale can flourish under a variety of conditions including poor soils, and cold and hot climates.

Some analysts, however, point to several factors will limited the spread and long-term success of the green revolutions. Thus, future increases in agricultural productivity may be limited by:

• The availability of fertilzers and water. New crops required huge amounts of fertilizers and water.
• Biological limitations. Plants have been far less responsive to genetic engineering than animals.
• Climate and soil limitations. Areas without enough rainfall or irrigation water or with poor soils cannot benefit from new varieties.
• Environmental degradation. Without careful land use and environmental controls, degradation of water and soil can limit the long-term ecological and economic sustainability of the green revolutions.

In the last few decades, many nations have also turned to the oceans to supply some of their food resources. Using various harvesting techniques, about 40 different species of marine organisms are caught for human and livestock consumption. Of these forty species, Cod, Herring, Jack, Mackerel, and Tuna account for over 60 % of the commercial fish harvested. From 1950 to 1990, the world catch of fish has increased by about 400 %. Because of this drastic increase, the numbers of some species of fish have declined substantially due to overfishing. In Canada, overfishing of North Atlantic Cod has caused the government to take extreme actions to stop the destruction of this fishery.

Another technique humans use to supplement their food resource from the sea, is fish farming or aquaculture . Fish farming involves cultivating aquatic species in a controlled environment. Usually the controlled environment is a floating cage, a pond or lake, or a fenced-in area of lake or ocean. In 1990, aquaculture supplied the world with 15 % of its seafood. Of this 15 %, three-fourths of it comes from LDCs.

Fish farming does create some ecological problems. For example, the development of shrimp farming in Southeast Asia is responsible for the clearing of millions of hectares of mangrove swamps. Mangrove swamps are the home to several thousand different species of plants, birds, reptiles, amphibians, fish, insects, and mammals.

3.2 Global Food Resources

Of the 350,000 species of plants cataloged by science only about one hundred crops are primarily used to feed the citizens of the world. About 15 plants and 8 animal species supply 90 % of our food. Wheat, rice, corn and potato are the primary crops that provide us with the bulk of the starch we consume. Other important crops, in order of production, include: barley, sweet potato, cassava, grape, soybean, oats, sorghum, sugarcane, millet, banana, tomato, sugar beet, rye, orange, coconut, cottonseed, apple, yam, peanut, watermelon, cabbage, onion, bean, pea, sunflower seed, and mango. Fruits and vegetables are valuable components of a healthy diet because they provide high levels of vitamins, oils, minerals, proteins and fiber.

Other foods consumed include fish, meat and animal products such as milk, eggs, and cheese. For most of the people on this planet meat and animal products, like milk, are too expensive to consume. As a result, 80 % of the meat and milk produced is consumed by only 20 % of the world's population. The raising of livestock on the Earth's land surface is creating some important environmental problems. Pasture and open range now occupies 24 % of the Earth's terrestrial surface and supports more than 3 billion domestic grazing animals. Over grazing by these animals is causing desertification, chemical and physical soil degradation, accelerated erosion, and plant biodiversity reductions.

Table 3.2 describes the countries with the largest areas in production of crops. The table also supplies information on amount of cropland per capita (1991), average percentage of land being irrigated (1989-91), average amount of fertilizer applied in kilograms per hectare (1989-91), average production of cereals (1990-92), and average cereal yield in kilograms per hectare (1990-92). The total amount of arable land worldwide is about 1,441 million hectares. The Russian Federation, which contains about 2.7 % of the Earth's inhabitants, currently cultivates about 213 million hectares or about 15 % of the world's cropland. Most of this production is sold to other countries or is used to feed livestock. The most efficient farmers are found in China. With 22 % of the world's population, the Chinese have to make do with only 6.7 % of the Earth's arable cropland. Yet, their population is well fed because intensive subsistence farming techniques produce yields equivalent to those produced in countries practicing industrialized farming. However, intensive subsistence agriculture requires large inputs of human labor, irrigation and fertilization in order to achieve these yields.

Most of the cereal production in the United States, Canada, Russian Federation and Australia is not used to feed humans directly. Most of this food is used to feed livestock which are used for dairy products, eggs or slaughtered for meat. This process of creating food is highly inefficient. As discussed earlier in this course, the efficiency of animals to assimilate food energy is less than 10 %. In fact, it takes about 16 kilograms of grain and soybeans to produce 1 kilogram of edible beef.

3.3 Industrial Agriculture and the Environment

As previously mentioned, modern day agriculture has been responsible for dramatically increasing the food supply. However, many of the practices used by industrial farmers can cause damage to nature or can be extremely limited by normal variablity in the environment.

3.3.1 Erosion and Soil Degradation

Recent increases in the human population have placed a great strain on the world's soil systems. More that 5.5 billion people are now using about 10 % of the land area of the Earth to raise crops and livestock. When used for such purposes, soils can suffer various types of degradation that can ultimately reduce their ability to produce food resources. Erosion is the number one factor degrading soils globally. Erosion is a process where wind and water facilitate the movement of top soil from one place to another. Water erosion is more detrimental to soils globally both by the volume of soil removed and area of land influenced. Soils are normally protected from erosion by the above- and below-ground parts of plants. Above-ground parts of plants, like stems and leaves, reduce the potential of wind and water to erode soils by acting as barriers to these mediums. Plants can also reduce erosion by binding and anchoring soil particles to roots.

Agriculture increases the risk of erosion through its disturbance of vegetation by way of land-use conversion, tilling or overgrazing. Many farmers prepare land by tilling or ploughing their fields to produce a smooth planting surface devoid or vegetation. This process, however, creates a soil surface that is very vulnerable to erosion. In Canada and the United States, some farmers have been using a technique known as conservation tillage or zero tillage to reduce the erosion problem. This technique uses special machinery and herbicides to plant crops with minimal disturbance to the soil surface.

The following agricultural practices lead to accelerated soil erosion:

• Overgrazing of animals (where more animals are raised than the forage can sustain). Trampling and eating diminishes the number of species grown in a particular forage area, and without adequate vegetative cover the land becomes more susceptible to both wind and rain erosion. Further when animals are grazed in riparian areas (areas next to streams) , the trampling near the stream banks causes erosion and stream sedimentation.
• Planting of a monoculture. This practice can lead to erosion for several reasons. First, a monoculture is harvested all at one time, which leaves the entire field bare and the natural rainfall is not retained by the soil and flows rapidly over the surface rather than into the ground. Secondly, if a disease or pests invade the area, the entire crop is usually wiped out and again leaving the bare soil susceptible to the elements.
• Row cropping. This agricultural practice is common with monocultures but can also be found in polycultures. This technique exposes the soil between each row of crops which is then vulnerable to erosion.
• Tilling or plowing. This is one of the oldest agricultural practices, it involves mixing up the nutrients within the soil, loosening the soil particles, incorporating oxygen and getting rid of weeds, however, it also increases the likelihood of erosion because it disturbs the natural surface and protective vegetation.
• Crop removal. The continuous removal of crops does not only increase the soil susceptibility to erosion due to exposure but it also increases it because the organic matter in the soil is depleted. Organic matter has the ability to absorb a lot of rainwater and without it, erosion is increased because water doesn't soak into the soil.
• Development of new land. This is a problem particularly in the least developed countries. Rising populations are forcing people onto marginal lands to grow crops. Hillsides are not developed properly, and are very vulnerable to erosion when water passes over them.

Many of these practices have resulted in degraded land across the globe. Slight degradation refers to land where yield potential has been reduced by 10 %, 10-50 % yield potential reduction is referred to as moderate degradation and severely degraded is land that has lost more than 50 % of its potential yield.

Problems of soil ersion can be stopped, and certain techniques can lead to soil enhancement and rebuilding. The techniques commonly used are:

1. Plowing style. The way in which a field is plowed can have a substantial effect on the amount of erosion that occurs. The following techniques are commonly used to reduce ersions:

a) Contour farming. This method involves tilling the field at right angles to the slope of the land. The ridges that are created act like a dam to hold the water while it soaks into the soil rather than running down the slope taking the soil with it. Contour farming has the ability to reduce erosion by up to 50%.

b) Terracing. This is another way of preparing the fields for planting and is usually used on much steeper slopes, by leveling off areas on the slope to prevent the flow of water down it. There are disadvantages to terracing however, in that the terraces themselves can be easily eroded and they generally require a lot of maintenance and repair.

2. Timing. The time which a field is tilled can have a major effect on the amount of erosion that takes place during the year. If a field is plowed in the fall, erosion can take place all winter long, however if ground cover remains until spring, there isn't as much time for the erosion to take place.

3. No-till Cultivation. Specialized machinery is available that can loosen the soil, plant seeds and take care of weed control all at once with minimum disturbance to the soil. Since all of these aspects are taken care of at one time there is less time for erosion to occur. There is a trade off though, weed and insect populations can increase which compete or destroy crops because they are not continuously being removed.

4. Farming Method. There are several ways in which a field can be cultivated in order to avoid erosion:

a) Strip Farming. This involves planting crops in widely spaced rows but filling in the spaces with another crop to ensure complete ground cover. The ground is completely covered so it retards water flow so that it soaks into the soil consequently reducing erosion problems.

b) Polyvarietal cultivation (where the soil is planted with several varieties of the same crop). As harvest times vary for the different varieties of the crop, results in protection from erosion because the entire field is not exposed all at once.

c) Trees act to protect against the mechanical damage and drying effects of the wind.

5. Adding Organic Matter. The addition of organic matter to the soil is important and can be achieved by plowing in crop residues or an entire crop grown specifically to be plowed into the ground (green manure). Microbes in the soil decompose the organic matter and produce polysaccharides which are sticky and act to glue soil particles together and help it to resist erosion.

Even though there are many, simple, methods for reducing erosion many farmers choose not to use them because short-term costs of implementing these practices outweigh the short-term benefits. For example, it is more expensive in terms of time and machinery required for a farmer to plant several crops on the same piece of land than it is to plant one single crop variety.

3.3.2 Fertilizer Use and Abuse

All plants require a certain quantity of nutrients to support growth. Macronutrients are nutrients which a plant requires in large quantities (such as carbon, oxygen, nitrogen and phosphorus). Micronutrients are also essential for plant growth but are required in much smaller doses, nutrients include iron, copper, manganese and zinc. Some of the macro and micronutrients are readily available from the environment such as carbon, hydrogen and oxygen. Others, such as nitrogen, have to be converted into a usable form for plants. Even though the atmosphere is approximately 78 % nitrogen, none of this can be used by plants directly, instead it has to be converted to such products as nitrate by the bacteria that live on roots and in the soils. The replacement of nutrients to the soil is very important because once a crop is harv ested the nutrients that it used for growth are permanently lost from the soil. If the same crop is grown repeatedly on the same field (as is done in conventional agriculture) many of the micronutrients are depleted such as boron, zinc and manganese. Other macronutrients, such as nitrogen, are often in short supply because they cannot be retained by the soil. Nitrogen, is one nutrient that plants require in large quantities as it is a major constituent of proteins and nucleic acids, however as mentioned earlier is often available in short supply.

Inorganic fertilizers were developed to increase plant yields by supplying plants with the necessary nutrients that are in short supply to stimulate growth. Inorganic fertilizers are commonly composed of nitrogen, phosphorus and potassium. Ammonia is not the sole form of nitrogen in fertilizers. Nitrogen can also be in the form of urea or ammonium nitrate, however ammonia must be synthesized first because it is used to prepare these other nitrogen forms.

Generally inorganic fertilizers have the benefits that they produce high yields, are easy to apply and are relatively inexpensive. The price, however, can vary because the production of fertilizer relies so heavily on oil and consequently its price in the world market. It is believed that approximately 25% of the worlds crops today are directly attributable to the use of inorganic fertilizers and due to this success, the demand for fertilizers has been doubling every 10 years.

Although inorganic fertilizer is responsible for dramatically increasing yields there are several drawbacks to its continued use:

Energy Requirements. The amount of energy to produce the nitrogen portion of the fertilizers is massive, taking almost 18,000 kilocalories of energy per one kilogram of nitrogen, using up a lot of the world's oil reserves. Phosphate and potassium also require energy for extraction but not nearly the extravagant amounts required for nitrogen production (3,000 and 2,300 kilocalories per kilogram respectively). There is concern, however, if projected increases in fertilizer use become reality it is believed that the potassium reserves will only last 107 years and the phosphate deposits only 88 years.

Organic Matter Decline. A big problem with inorganic fertilizers is that they do not replace the organic matter in the soil that is lost when a plant is harvested. Organic matter is very important in the soil for a number of reasons. It modifies the soil structure by preventing compacting and maintains pore spaces for water and air movement to the roots. It's decomposition product, humus, lowers the soil pH releasing nutrients that are available in the soil for plant uptake. Organic matter is also an important energy source for bacteria which are vital in the carbon and nitrogen cycles.

Greenhouse Effect. Research has demonstrated that fertilized fields emit 2 to 10 times as much nitrous oxide as unfertilized soils and pastures. Emission rates are increased in temperate climates. In addition, the use of fossil fuels for the production of ammonia emit carbon dioxide into the atmosphere a very important greenhouse gas.

Leaching. Many farmers apply more fertilizer to the crops than can be taken up by the plants. Nitrogen is the most susceptible to leaching because it cannot be retained by the soil. Phosphates can react with other minerals in the soil forming insoluble compounds and the amount of potassium leached is influenced by the cation exchange capacity of the soil. These excess nutrients can contaminate ground water and surface water. Nitrates in the drinking water can be harmful and are thought to be carcinogenic. In surface waters, fertilizers can stimulate growth of algae and other aquatic plants, when these plants die they consume oxygen ultimately leading to eutrophic waters.

Health Hazards. Some nitrogen containing fertilizers are hazardous to human health. Ammonia, for instance is toxic and can be very reactive with some substances. Ammonium nitrate, another common fertilizer is explosive so extreme care must be taken during manufacturing and storage.

Total dependency on chemical fertilizer not only changes the chemical, physical and biotic properties of the soil, but is endangering other environmental aspects. There are several ways to reduce the damage being caused by inorganic fertilizers:

Reduce Leaching. One method to reduce leaching losses of fertilizers (and subsequently protect water resources) is to apply inorganic fertilizers at a rate which is equal to plant uptake. This involves applying small quantities of fertilizers several times over the growing season to allow the plants to use them rather than apply them all at once at the beginning.

Green Manure. The concept of green manure is growing some sort of vegetation on the field for the sole purpose of plowing it into the ground. This not only increases the amount of organic matter in the soil which has numerous benefits but it also increases nutrient availability to the next crop that is grown there.

Use Animal Fertilizers. Animal manure is a cheap fertilizer source especially if the animals are already on the farm. The nutrients are released slowly into the soil for plant uptake and it also increases the organic matter in the soil. Animal fertilizers have the disadvantage that they generally don't contain a lot of nitrogen and sometimes release of other nutrients is too slow.

New Crop Biotechnology. Scientists are trying to develop new strains of crops to fix their own nitrogen (a trait of legumes). If researchers are successful then the demand for nitrogen fertilizers would be greatly reduced as they would no longer be required.

Crop Rotation. By rotating the field with different crops reduces the amount of nutrients depleted because different plants require varying amounts of nutrients. Fields that are planted with corn or cotton (crops that remove a lot of nutrients, especially nitrogen) one year should be replaced by legumes or some other crops which have the ability to replace nutrients.

Intercropping. Intercropping involves growing two or more different crops on the same piece of land. Crops such as corn which depletes soil nitrogen can be planted right along side legumes which replenish it, again reducing the need for any chemical fertilizer inputs.

3.3.3 Pesticide Use and Abuse

3.3.3.1 Introduction

A pesticide is a substance, or mixture of substances, that is used in the control of pests. Pesticides include all materials that are used to prevent, destroy, repel, attract, or reduce pest organisms. A pest is any living organism which has the ability to harm people or damage property. Therefore, pesticides are used in many different applications such as forestry, landscaping, agriculture, and domestic use. Examples of pests include plant parasitic viruses, bacteria, nematodes, fungi, insects, weeds, rodents, and birds. Many of these pests cause extreme damage to various agricultural products resulting in various economic losses.

Pesticide use has been prevalent for thousands of years. Ancient Romans demonstrated the use of pesticides by burning sulphur in an attempt to control insects. The early Chinese civilization controlled the pests of crops by using arsenic and pyrethrum. They also used ground tobacco to control the aphid population. During the 19th century in France, a copper-lime mixture was used to control mildew on crops. Pesticides first became widely used in the beginning of the 20th century with the development of intensive agriculture. By the early 20th century, two classes of pesticides were primarily used. These included botanicals, natural chemicals derived from plant material, and inorganic salts which were widely used as fungicides, herbicides and insecticides.

Before World War II, only a few synthetically produced pesticides were used including DDT, dinitrophenols, hydrogen cyanide, naphthalene and methyl bromide. Since World War II, a large number of synthetic organic pesticides have been developed, and now over 600 basic pesticides and chemicals have been incorporated into over 5000 brand name products which have been registered for use in Canada. The discovery of DDT in 1934 (dichloro-diphenyl-trichloroethane) was a major advance in chemicals which possessed insecticidal properties. This chemical was highly toxic to insects, relatively non-toxic to mamals, inexpensive, stable, soluable in water, and easily sprayed of infested areas. Its early use was especially beneficial in World War II in tropical areas where disease and parasites took their toll on soldiers. Okanagan fruit growers used the pesticide DDT in the early 1940s to fight infestations of codling moths. However, by the 1960s the codling moth began to show r esistance to DDT and other methods of control had to be implemented. The use of DDT in Canada and the United States was eventually banned because of its persistence in the food chains of lower animals and its damage to bird life.

Globally, about 2.5 million tons of pesticides are applied annually to control pest organisms. Most of this application is targeted on agricultural crops. Pesticides make a significant contribution to increasing agricultural production. Pimentel et al. (BioScience 42(10): 750-760) estimate that for each dollar invested in pesticide control about four dollars of crops is saved. Pesticides also have many risks associated with their use. These risks include human health effects, livestock animal poisoning, beneficial insect losses, water contamination, wildlife losses, and the genetic evolution of pesticide resistance.

3.3.3.2 Types of Pesticides

Pesticides can be classified according to their chemical structure:

Inorganic pesticides are broad-based poisons made from common natural chemicals like arsenic, copper, lead and mercury. These chemicals are generally highly toxic and indestructible. Because of these two features, these chemicals can accumulate in the environment.

Natural or organic pesticides are generally compounds extracted from plants. Many plants, like tobacco, chrysanthemum, and conifers, have evolved the ability to produce secondary substances that are used to deter herbivore consumption.

Fumigants are specific compounds in gaseous form that are used to sterilize soil and prevent pest infestation of stored grain. The use of these chemicals has been banned or reduced in many parts of the world because of the extreme danger associated to workers with their application.

Chlorinated hydrocarbons are synthetic organic compounds that effect the nervous system of the pest. They include such chemicals as DDT, chlordane, alrin, dieldrin, toxaphene, paradichlorobenzene, and lindane. These chemicals are highly resistant to decomposition and can remain in ecosystems up to 15 years.

Organophosphates are synthetic chemicals that have been developed as a by-product of human nerve gas research during World War II. These chemicals are 10 to 100 times more toxic than chlorinated hydrocarbons to animals larger than insects. However, their persistence in the environment is quite short, usually in the order of hours to days. Some examples of organophosphates include parathion, malthion, dichlorvos, dimethyldichlorovinylphosphate (DDVP), and tetraethylpyrophosphate (TEPP).

Carbamates are urethanes that effect the nervous system of pests. They are very similar to organophosphates, and include such chemicals as carbaryl (Sevin), aldicarb (Temik), aminocarb (Zineb), carbofuran (Baygon), and Mirex.

Microbial agents are living organisms that are used to control pests. Some examples of microbial agents include lady bugs, parasitic wasps, virus, and specific forms of bacteria.

3.3.3.3 Pesticides and the Environment

Up to 90 % of the pesticides applied never reach the intended targets. As a result, many other organisms sharing the same environment as the pests are accidentally poisoned. Human pesticide poisonings are clearly the most ontroversial. In 1989, the World Health Organization and United Nations Environmental Program released the publication ' Public Health Impact of Pesticides Used in Agriculture' which reported that there are about 1 million human pesticide poisonings and 20,000 deaths each year. Many other types of non-pest organisms are also adversely effected by pesticide application. During the 1950s and 1960s several species of birds, including osprey, cormorant, brown pelican, bald eagle, prairie falcon, sparrow hawk, and peregrine falcon, were severely effected the pesticide DDT. Scientists discovered that a chemical derived from the DDT weakened the egg shells of these birds, reducing their ability to reproduce. In the US, estimates suggest that 20 % of honeybee colonies are eradicated by pesticide application.

3.3.3.4 Pesticide Contamination: Water Resources

Contamination of groundwater and surface water by pesticides is a very common problem. Some of the important factors that influence the degree of contamination include:

• Permeability of the soil between the surface and groundwater table which affects the movement of water and pesticides toward the ground water.
• Physical properties of the soil may impede or influence the movement of pesticide contaminated water to groundwater
• depth of groundwater from the surface.
• Slope of the ground surface which controls the direction of runoff movement, shorter steeper slopes increase the likeliness of contamination.
• Distance of the pesticide application area to surface water.

Pesticides can reach water resulting from direct treatment used to control pests, or indirectly. Pesticides can contaminate aquatic systems by fallout from aerial sprays, soil erosion, or through the disposal of pesticide containers or effluent from pesticide factories. Those pesticides which are soluble in water may be carried by nearby waters by surface runoff. 0.5 to 15 % of a pesticide treatment can be carried into an aquatic system due to runoff from agricultural land. Waters are also contaminated through pesticide drift during application, and atmospheric fallout on rain and dust.

Once the pesticide reaches the water system, its distribution and fate will depend on its persistence and solubility Most pesticides that persist in a water system usually become adsorbed (bound to the soil particle) onto floating particles and settle out as sediment. Some pesticides may remain here for a number of years and may re-enter the water due to the disturbance of sediment. Generally, the more persistent a pesticide is, the greater the effect it will have on the aquatic ecosystem. Also, the more soluble a pesticide is , the greater its potential is for aquatic system and groundwater contamination. The persistence of a pesticide in water depends on the nature of the water it is in. Factors affecting the persistence of a pesticide in a water system include water composition, pH, temperature, aquatic life present and amount of suspended organic and inorganic material.

The results of pesticide contamination of water systems, both surface and groundwater are the organisms living in and using the water are affected such as humans, domestic animals, fish, birds, plants and wildlife. Many modern pesticides are particularly toxic to water-dwelling insects, plankton, crustaceans and fish.

Agriculture Canada has reported that soil in the Okanagan area is generally low in organic matter. This increases degradation time, and decreases the degree to which the pesticide decays before it is transported from the soil layer to parts of the hydrologic cycle. The net result of this process is generally higher contamination levels in groundwater and surface water in lakes and rivers.

3.3.3.5 Pesticide Contamination: The Atmosphere

There are many ways in which pesticides reach the atmosphere. These include: spray drift during application; volatilisation during application; volatilisation from treated surfaces; escape from pesticide manufacturing and formulating plants. The amount of drift is a function of atmospheric conditions, application equipment, the pesticide being applied, and the height of release of the pesticide. Volatilisation of secondary deposition can also occur where the water droplets or dust particles which have returned to the Earth are subject to evaporation once again. Although pesticides can volatilize into the atmosphere from water surfaces, volatilization generally occurs soon after application.

Many studies have demonstrated that pesticides are in the atmosphere are present as either particulate matter or in the vapour phase. The inhalation of these pesticides can be toxic for many organisms.

The ultimate fate of pesticide residues in the air is poorly understood, but evidence suggests that these residues are globally transported over long distances, carried into the upper atmosphere, or fall back to the Earth in precipitation. Some pesticide residues may also be broken down by light in the upper atmosphere.

3.3.3.6 Pesticide Contamination: The Biosphere

Over the last few decades, the variety and amounts of pesticides have greatly increased, resulting in some beneficial effects on the agricultural industry. However, there have been many reported cases of wildlife kills due to improper pesticide use. There is concern of the effects of pesticides on wildlife due to direct effects as well as long term exposure to low levels of pesticides. This exposure may cause death or result in sublethal effects. Sublethal effects do not cause mortality, but reduce the population through sterilization effects or weakening of the organism resulting in its inability to escape from prey. Pesticides may also alter the physical habitat of many organisms or damage food sources. Once one species in an ecosystem is altered by pesticides, many other species will also be affected due to the high level of interactions within the ecosystem.

Pesticides are often concentrated within food chains as these chemicals are passed from one organism to another as the result of consumption. Because of this process, pesticides tend to accumulated in large organisms that do a lot of consuming. Birds appear to be the major targets of pesticide pollution in almost every type of ecosystem. The types of birds that are particularly affected are those at the top of the grazing food chain. This includes birds of prey like eagles, hawks, and owls. Plant, insect, and grain-feeding birds are also susceptible. It is very difficult to protect birds from pesticide poisoning, especially when highly toxic pesticides are used. Chlorinated hydrocarbons have been implicated in the decline of several bird populations by interfering with their reproductive process. This is caused by either delayed breeding or the discontinuance of egg-laying. Eggs that are laid are thin and easily broken, leading to high mortality rates.

There have been many adverse effects of pesticides on birds that have been reported in the Thompson-Okanagan. Bird populations found living in habitats in and adjacent to orchards have frequently been found exhibiting the harmful effects of pesticides. When DDT was used, along with other organochlorine pesticides, the breeding success of predator species, such as osprey and peregrines decreased. More recently, a study was performed by the Canadian Wildlife Service on pesticide residues in wild bird eggs. This study was done on swallows and bluebirds in 1990, and quail and pheasants in 1991. It showed that the levels of a breakdown product of DDT, called DDE, were 10 times higher in the eggs of the birds from the Penticton-Naramata area than the control area. Even though DDT has been banned for years, this pesticide and its breakdown products still persist in the environment, and have not yet disappeared.

Another type organism often poisoned by pesticides is fish. Fish kills have resulted from agricultural contamination of waterways due to atmospheric fallout, drainage, runoff erosion, and from the discharge of industrial effluents containing pesticides into the waterways. Also, many of the organisms on which fish feed are susceptible to pesticide poisoning, which may affect the fish population.

When pesticides are applied broadly outdoors, there is a great danger of poisoning honeybees, wild bees or other beneficial insects. This can result from:

• The drift of pesticide sprays or dusts onto nearby crops or weeds that are currently in bloom.
• Application of pesticides to crops during the blooming season.
• Contamination of flowering cover crops and weeds during orchard spraying.
• Contamination of water, pollen or nectar.

Large economic losses may result from weakened hives or reduced honey production due to pesticides application. Also, some bees are extremely important in the pollination of specific crops and wild plants, and are therefore very beneficial

3.3.3.7 Pesticide Contamination: Humans

The environmental effects of pesticides on wildlife, soil and water all strongly impact the quality of human life. Pesticide residues may also cause contamination of drinking water and food. There have been many reports of small pesticide residues in various foods. Over the last 50 years many human illnesses and deaths have occurred as a result of pesticide contamination, up to 20,000 deaths per year. These are mostly due to accidental exposure of farm workers and sprayers to pesticides. Accidental exposure may result from improper handling, or the use of insufficient protective clothing when applying pesticides.

One potentially very harmful effect of pesticide use is the ability of pesticides to interfere with the endocrine system (which produces hormones) and the immune system of animals and humans. The concentration of pesticides required to cause this type of damage can be very small, leading to increasing concerns involving pesticide use.

Almost all pesticides can be fatal if present in large enough quantities, but organophosphates are found to be the most harmful and toxic. Small amounts of chlorinated hydrocarbons have been found to be present in the body fat of humans. The main source of this is contaminated food. Long-term effects of pesticide exposure can lead to cancer, mutations and congenital defects.

3.3.3.8 Alternatives to Pesticides

There are many alternative methods to pesticide use which are less damaging to the environment. Some of the more common methods include:

Mechanical/Physical Control - hand-picking, screens or traps, electricity, light, heat, or cold storage.

Cultural Control - the manipulation of the environment to produce conditions which are less favourable for pests.For example, orchards can be cleaned of drying wood which is a breeding ground for wood infesting beetles; soil tillage can be used to interfer with the life cycles of insect pests. The rotation of crops can eliminate pest species which survive year after year on the same crop.

Biological Control - involves the release or enhancement of predators, parasites, or diseases to control or manage a population of pest species.

Regulatory Control - this involves an attempt to regulate commerce, farming, and other human activities that affect the distribution and prevalence of destructive insect pests. This type of control has the ability to slow down the movement of insect pests until research can develop adequate control measures.

Integrated Pest Management ( IPM) - currently is the most common alternative to the use of pesticides being used. IPM is an approach to crop protection which combines a number of techniques in an organised fashion in an attempt to suppress pest populations. This management is generally accepted as the most desirable and effective approach to protection from insects, mites, disease, weeds, and other pests. The aim of IPM is to prevent economic loss resulting from pests as well as to avoid harm to people, non-target organisms (plants and animals) and the environment. However, the object of IPM is not to control 100 % of the pests in an area.

IPM is needed due to the over-reliance on pesticides that has developed since their rapid emergence. This over-reliance has lead to contamination of the environment and the development of pesticide resistant species.

The IPM method involves several steps which are listed below:

• Identification of the problem. The more information that is known about the target pest organism, such as the biology of the organism, the behaviour, enemies and life cycles, the more effective the treatment will be.
• Monitor the pest populations. This provides the information needed to make decisions about the timing of treatments and the necessity of them.
• Establish the injury level or the unacceptable level of damage from a particular pest. This level is usually the economic injury level when dealing with agricultural crops.
• Establish the action level. When the action level is reached the particular treatment is applied to prevent the injury level from being reached.
• Develop treatment plan. One treatment or a combination of several treatments are co-ordinated into a program to control the pest organism. This may include the combination of biological controls, cultural controls, physical or mechanical controls, or use of a low level of chemical controls.
• Evaluation of the pest management program. This is necessary to determine the success or the IPM program, so improvements can be made and the benefits can be determined.

Generally in IPM programs, pesticides are used only if their application is absolutely required. If they are used, the pesticides are usually of low toxicity and break down quickly in the environment. They are also applied as efficiently as possible.

Various IPM programs are extensively used the tree fruit production in the Thompson-Okanagan area. All of these programs differ in the number and types of controls which have been integrated.

• Orchard mite control using IPM involves application of dormant oil, regular assessment of pest and predatory mite numbers, only necessary miticide application avoiding chemicals which are highly toxic to the predators of the target mites.
• IPM of fruit tree and European leafroller involves monitoring, application of a chemical and/or biological control treatment if needed, and proper pruning for removal of eggs and for effective spray penetration.
• The pear psylla IPM program involves the application of dormant oil, preservation of natural enemies through reduced pesticide use or the use of less toxic pesticides, and monitoring psylla and natural enemies to assess the need and the timing of spray. Pear Psylla has been heavily damaging Okanagan pear crops to the point that growers maintain it could cause the pear industry to be wiped out unless these types of IPM programs are introduced. Psylla causes fruit rusting leaf blackening and affects fruit size.
• Orchard floor vegetation should be monitored to minimize rodent damage and nutrient and water competition to fruit trees. The orchard floor vegetation may also provide a habitat which is suitable for the natural enemies of potential fruit tree pests.
• IPM is also used for control of the codling moth in the apple and pear orchards of the Thompson-Okanagan region.

IPM is becoming more and more accepted as both an environmentally and an economically preferable approach to pest management. A move is being made away from conventional pesticide use to a more environmental friendly approach to pest management. British Columbia is one of the world leaders in the development and application of IPM programs.

3.3.4 Irrigation and Water Pollution

Irrigation in combination with inorganic fertilizers and pesticides have resulted in dramatic increases in crop yields in the twentieth century. The quantity of water that is being used for irrigation is threatening the world's fresh water supply not to mention degrading soils. Data has shown that between 1960 and 1980 the spread of irrigation was responsible for almost 60% of the massive increase in agricultural output in developing countries. In addition other agricultural practices are having a huge impact on the aquatic environment.

Water use. Many crops are being grown in climates that could not otherwise support them largely due to the developments in irrigation. Irrigation systems only average a 40% efficiency rate, with the remaining of the applied water being lost to evaporation, runoff, infiltrating below the root zone or seepage from unlined canals before it even is applied to the fields. This low efficiency in combination with dramatic use has depleted water supplies in many areas.

a) Ground water. Many farms that do not have streams or rivers nearby rely on ground water for irrigation purposes. Numerous aquifers, however, are in danger of drying up do to overuse by so many people. A good example is the Ogalla aquifer in the Southern United States which has over 175,000 wells tapped into it, irrigating over 15 million acres of land is being depleted at a much faster rate then its natural rate of recharge. Texas is removing water from this aquifer at a rate 40 times higher than it can naturally be replenished.

b) Surface water. For irrigation purposes, rivers and streams are diverted from their natural courses. Lowering water levels in rivers and streams can alter habitats so that aquatic life can no longer survive there. A dramatic example water diversion is the Aral Sea in the Soviet Union where diversion of water from rivers and streams running into it has reduced the sea to one sixth its 1960 size and all native fish species have disappeared.

Salinization. Farmers generally have a tendency to over irrigate their crops to ensure that they are receiving enough moisture, this practice, however, can increase salinity both in the soil and in water supplies.

a) Soil salinity. When crops are over irrigated, the surplus water evaporates and the salts that are dissolved in it are left behind increasing the salinity of the soil. Increased soil salinity can cause a decrease in plant productivity and interferes with water uptake by plants. Fruit crops are the most sensitive to soil salinity followed by vegetables and then field and forage crops. Generally the problem is inadequately solved by flushing the root zone with excess water, which generally ends up contaminating the ground water or irrigation canals. The water is then reapplied to crops either on the same field or somewhere else downstream resulting in the same problem over again.

b) Groundwater salinity. Irrigation does not only cause increases in soil salinity, it can also increase salinity in ground water. Water at the bottom of an aquifer rests against bedrock (which contains salt) so it generally is more saline than water above it. As water is withdrawn from the aquifer it approaches an area of increasing salinity, resulting in the previously outlined problems.

Waterlogging. This results when soils are over irrigated. Generally waterlogging occurs in areas that have clayey soils or an impermeable layer of clay that lies beneath the surface, so water cannot move efficiently through the soil and cannot adequately be drained. Eventually the soil root zone becomes saturated with so much water that plant roots can no longer obtain adequate amounts of oxygen for growth and the soils are no longer suitable for cultivation.

Sediment. Sediment is the largest surface water pollutant by volume and is the result of erosion. Intensive irrigation can cause increases in erosion rates and the therefore increasing sediments loads of streams and rivers. This is especially a problem when crops are planted on slopes. Also overgrazing on riparian areas (areas adjacent to streams) can result in erosion and increased stream sedimentation. Biologically, increased sedimentation can smother organisms, destroy wildlife and spawning areas, threaten fish populations as temperatures are generally increased, reduce the amount of light available for photosynthesis which causes a chain reaction as food resources are limited. Physically, sediments can fill reservoirs to a point where flooding occurs. Sediment can also carry pesticides and fertilizers with it, contaminating the water ways.

Pesticides. Pesticides can enter groundwater by leaching through soils, they can be washed away with run-off or eroded with sediments into surface waters. Once in the waters there are several problems that the pesticides cause:

a) One of the big problems is that pesticides are persistent (they don't easily break down) in the environment. As a result of this persistence, pesticides can easily accumulate in food chains (DDT is one such chemical which does this but it has now been banned for use).

b) Pesticides can inhibit plant photosynthesis, interfere with reproduction, respiration, growth and even kill aquatic life.

c) Most water treatment plants are unable to remove pesticide residues so they remain in the drinking water and can threaten human health. They can cause flu-like symptoms, some are carcinogenic and some can threaten infants genetic structure.

Fertilizers. Farmers generally apply too much fertilizer to their crops and this excess, particularly the nitrates can by easily leached into lakes, streams and ground water. It can also be washed away with runoff or eroded with sediments. Fertilizers can also have numerous affects once in the water:

a) Fertilizers stimulate the growth of algae and other aquatic plants. When increased aquatic vegetation dies, it consume a lot of the oxygen causing the lake to become eutrophic, and changing the biota that was found there.

b) When excessive amounts of nitrates are found in drinking water it can be dangerous to humans, it can lead to blue baby syndrome and it is believed that nitrates many be linked to stomach cancer.

Agricultural practices can be altered in several ways to reduce the impacts that it has on the aquatic environment:

Saving water. There are several methods that can be used to reduce the amount of water that is being applied to crops yet still ensure that the crops are receiving enough water for optimum growth.

a) Trickle or drop irrigation. This technique involves delivering water directly to a small area adjacent to individual plants rather than applying it to the whole field where it can runoff or evaporate. This not only reduces the amount of water required but it also results in less erosion and it reduces the likelihood of soil salinization because water is only applied to the plant directly as needed.

b) Plowing techniques. The way in which a field is plowed can reduce the amount of water used. When a field is contour plowed the ridges act to hold water so that it can be soaked into the ground, terracing the land can also lead to the same results.

c) Crop types. Planting crops that are suited to local climate reduces the amount of water required. If the climate is dry, then crops such as wheat should be planted because they are a lot hardier when compared to corn which requires a lot of water.

Fertilizer alternatives. One change that could potentially alleviate a lot of problems is to switch from chemical fertilizers to organic fertilizers. Organic fertilizers release nutrients at a slower rate and plants can uptake them, they increase the ability of the soil to retain water and hold soil particles together both which lead to decreased erosion and consequently decreased sedimentation. Other changes include intercropping or crop rotations both which reduce the need for inorganic fertilizers.

Pesticide alternatives. The use of pesticides can be reduced by rotating crops so that pest do not establish themselves or by multicropping where crops are planted with plants that have natural defenses against pests or that support predators of pests.

In British Columbia, several different types of irrigation are used depending on the crop and the area. Irrigation types include flood, handmove, wheelmove, solid set, traveling guns, center pivots and trickle irrigation. Even though trickle irrigation is one of the most efficient methods for irrigating crops, it is only used in 3% of the cases, the abundance of fresh surface waters in this province hasn't resulted in the need for this type of irrigation yet. Compared to the rest of Canada, British Columbia and the Prairie Provinces account for almost 92% of the irrigated land.

3.3.5 Energy Use

Industrialized agriculture requires energy for almost every aspect of food production. Industrial agriculture substitutes the by-products of energy use for both human labor and land and can increase yields by well over 100 % when compared to traditional methods. This increase in productivity, however, requires an increase in fossil fuel use by approximately 400 %. Some agricultural economists believe that the continued expansion of industrial agricultural methods into LDCs is manditory in order to meet the food requirements of their expanding populations. Environmentalist, on the other hand, suggest that this may not be possible because of the finite supply of fossil fuels and because of the costs of the environmental damage due to this method of agriculture.

As mentioned in the previous paragraph, industrial agriculture requires large amounts of fossil fuel use. The following list outlines some of the main industrial agricultural activities that consume fossil fuels:

Production of Nitrogen Fertilizers. It is estimated that almost one third of the fossil fuel used in industrialized agriculture is consumed by the production of nitrogen-based fertilizers. The production of nitrogen fertilizers requires large amounts of natural gas for the synthesis of ammonia. Nitrogen is commonly the most limiting nutrient to plant productivity, and most intensive farming systems use large amounts of this nutrient to increase yields per hectare. Some estimates suggest that traditional farming systems in Africa could triple their productivity with fertilization. Savings in energy can be accomplished by:

• Applying fertilizers more carefully to crops to reduce over fertilization. Europeans use twice the fertilizer as compared to the average North American farm without any difference in crop yields. This data suggests that Europeans are applying too much fertilizer to their fields. More efficient analysis of soil nutrient status and crop needs could reduce the problem of over fertilization.
• Changing the method of application to the crop. In general, surface applications of fertilizer only get 30-40 % of the nitrogen applied to the crop. Using more efficient methods, like sub-surface banding, could significantly reduce losses to the environment.
• Using crop rotations. The planting of legumes (peas, beans, vetch, alfalfa, and leucaena trees) on alternative years can be used to re-charge the soil with nitrogen naturally.
• Increasing the use of organic fertilizers. In China, the efficient use of organic nutrients from animal wastes, compost and green manure greatly supplements the use of inorganic fertilizers.

Irrigation. In the United States, 13 % of agricultural energy consumption is used to pump water, primarily from groundwater sources, for irrigation. Energy consumption could be decreased in this process by employing more efficient irrigation systems that reduce loss of water.

Mechanical Tillage of the Soil Surface. Tillage and seedbed preparation consumes large amounts of energy for the operation of machinery. The diesel fuel consumption for plow-based conventional tillage systems ranges from 60-80 litres per hectare. New techniques, like conservation tillage, have been developed where the application of herbicides and the use of specially developed seeding machines can replace the tilling process. This switch to this technology could reduce energy consumption significantly. This technique also benefits the soil by improving its structure and moisture holding capabilities.

Livestock Raising. Raising livestock requires enormous quantities of fossil fuels. Energy is required for growing, harvesting, processing and transporting animal feed, handling manure, and maintaining climate controlled surroundings. Fuel savings could be produced by developing more efficient means of livestock keeping and by reducing the consumption of meat and other livestock products.

Food Processing. A lot of energy is required to store, process, package, transport, refrigerate and cook both plant and animal farm products. Studies in industrialized countries have revealed that for every calorie of food consumed, on average, 10 calories of energy are used to produce, process and package the product. For comparison sake, one unit of human labor energy expended by the traditional farming techniques results in approximately one unit of food energy for consumption.

Modern energy intensive agriculture can continue to expand for perhaps several more decades. However, with depleting oil reserves, energy prices are likely to escalate to a point where their use in industrial agricutural systems will be too expensive. Several things can be done now to minimize the use of fossil fuels. Farmers can begin to use local perpetual and renewable energy sources including wind, water, sun, animal and crop wastes. Agricultural systems can also be made more energy efficient. Some studies suggest that the application of organic farming techniques can reduce energy use by more than 40 %.

3.3.6 Habitat Destruction and Biodiversity Reduction

Monocropping is a technique which is used by almost all industrial agriculturists. This process of planting only a single crop can lead to disastrous effects, not only in terms of erosion and loss of soil fertility, but it has a profound effect on the biodiversity of an area.

Many different species are disappearing from the planet, being replaced by crops that are genetically uniform and have large yields. India once cultivated over 30,000 different varieties of rice, but today over 75 % of production comes from fewer than 10 varieties. Vegetation is also disappearing quickly in the tropical rainforests, where slash and burn agriculture is common. The land is stripped of its native vegetation and replaced with cash crops or livestock which end up being sold to the MDC's (most developed countries). Many of the species being wiped out only grow in these areas so are permanently lost.

Loss of biodiversity can result in:

Reliance on hybrid seeds. Hybrid seeds can be planted, tended and harvested efficiently. They are genetically uniform, so an entire crop is vulnerable to pests, disease, flood, and drought. As a result, what effects one plant will effect the others in the same fashion. If there was genetic variety within the crop, some plants may be wiped out by one of these factors but it is likely that not all of them would be.

Species that are disappearing may have traits that could be used by scientists to engineer new crop strains. For example, some of the crops disappearing now may have been drought tolerant, a gene which could have been integrated into a different species. Such reductions in biodiversity limits the potential for future green and gene revolutions.

Scientists have recognized the problem of loss of genetic diversity and have established seed banks to save remaining varieties. Many crops, however, are disappearing faster than they can be located, collected and stored in the seed banks. There are several problems with preserving crops in seed banks. Firstly, seed could be lost due to a fire, power failures or unintentional disposal, permanently destroying all collected seeds forever. Finally, research has shown that when a plant is reintroduced into its native area it may not do as well as it previously did do to changes in soil, flora and climate of the area as the plant stopped evolving when it went into storage.

Farmers can also help to avoid the problems that coincide with loss of biodiversity by simply cultivating either several varieties of the same crop (polyvarietal cropping) or several different species (intercropping), which limits the likelihood of all plants dying due to a flood, disease, pests, etc. Acceptance of non-traditional crops for food sources would also help retain genetic diversity, such as the cocyam from West Africa and Latin America which is as nutritious as a potato.

3.4 Sustainable Agriculture

A sustainable agricultural system involves the modification of agricutural techniques in both existing industrialized and traditional agricultural systems in order to provide for the needs of current and future generations while conserving natural resources. In order for a agricultural system to be called sustainable the following requirements must be met:

• Soils conservation must be reached. In other words the soils cannot be degraded by erosion, salinization, water logging or loss of soil fertility.
• Water resources must be managed so that they are preserved yet still meet crop needs.
• The system must be economically viable.
• The biological and ecological integrity of the system must be preserved.

In order to achieve these requirements, a sustainable agricultural systems incorporates parts of industrialized, traditional and new agricultural systems in order to take advantage of local climates, soils and resource systems. With such a wide variability in climate, soils and resources results in there being no exact way to characterize sustainable farming, because each field has different requirements. There are many ways to meet the goals of sustainable agriculture, many of which are outlined as alternatives to some of the problems with industrialized agriculture. There are some concepts, however, that are common to all sustainable farms:

• Crop rotations. This is a central component of almost all sustainable farming systems. It involves the succession of various crops growing on a field. Rotating crops has many benefits to the farmer including a natural weed and insect control and efficient nutrient cycling to name a few. It has been found that when crops are rotated yields are 10-15% above those of monocultures.
• Organic matter. Adding organic matter to the soil is yet another essential constituent of sustainable agriculture. This improves soil structure, enhances fertility, increases water storage capacity and promotes the tilth (physical condition) of the soil making it easier for plants to emerge from the soil and extend roots downward.
• Plant nutrients. To reduce the use of inorganic fertilizers, sustainable systems tend toward biological sources for plant nutrients. Green manure, where a crop is grown specifically to be plowed into the ground not only increases the present organic matter, but it also supplies many nutrients back to the soil, increasing plant productivity.
• Increase biological diversity. Emphasizing small to medium scale production of a diverse mix of crops, increases biological diversity. This can result in increased soil productivity which means less inorganic fertilizers are needed, reductions in soil erosion and reductions in pesticide use as crops that can be mixed that provide a habitat for predators of pests. This practice can also protect farmers from economic hardships due to the flooding of the market with a particular crop or the wiping out of a crop from a disease.
• Integrated pest management (IPM) is another common aspect of sustainable farming which integrates both biological, mechanical and chemical methods to control pests while minimizing the affects to the environment.
• Minimize fossil fuel use. When available, local perpetual and renewable energy sources such as the sun, wind, water and animal crop wastes should be used, rather than depending on non-renewable fossil fuels.

In conclusion, sustainable farming, not only minimizes the influence of farming on the environment but it also gives farmers more control over their livelihood. Application of sustainable agriculture practices results systems that are less prone to weather and changes in the marketplace. It also cuts costs of running a farm by requiring lower applications of inorganic fertilizers and pesticides. Yields from sustainable farms are generally lower than those of conventional systems. However, profits in the long-run can be higher because lower input costs and reduced environmental damage.

3.5 Agriculture in the Thompson-Okanagan

The history of agriculture in the Okanagan spans nearly 150 years. The earliest attempts at agriculture in this region were directed at raising cattle and growing grain. By 1892 over 20,000 head of stock were being tended to by some of the first 400 settlers in the valley. In the 1890s, the first apple orchards were established. During that same decade, hops were also planted, but were later abandoned for economic reasons. Tobacco was grown on a large scale in the valley at the turn of the century, but it too had to be abandoned in the 1930s because it was economically not viable. In the 1920s, grapes were grown, first as a fruit crop and then later for the production of wines. By 1985, the Okanagan and Similkameen Valley's contained 90 % of British Columbia's orchards and 95% of the province's vineyards.

From Vernon south to the U.S. border, the Okanagan's climate is ideal for growing fruit trees and grapes. It has mild winters with plenty of snowfall for the protection of dormant trees and vines, cool springs that delay budding, and long hot growing seasons that encourge excellent fruit development. However, insufficient rainfall occurs during the hot summers and crops growing in this climate must be supplied with additional water from irrigation systems. Slight variations in micro-climate throughout the valley cause different fruit crops to be grown in certain locations. In the south, slightly warmer climates favor the growth of soft fruits like cherries, apricots, and peaches. Slightly cooler climates occurring between Penticton and Vernon best suit hardier crops such as apples. North of Vernon, the soils and climate are better suited for dairy farming.

Agricultural methods in the Thompson-Okanagan are primarly industrial in nature. This type of agricultural system relies on the extensive use of irrigation, fossil fuels, fertilizers, and pesticides to achieve high levels of productivity. The Thompson- Okanagan is also experiencing some of the highest population growth rates in the provience of British Columbia. As a result of these two factors, the following environmental problems have or will develop:

• Because of rapid population growth and land-use change, the size and number of farms is declining significantly. The problem with declining farm space is that there are only two significant areas in Canada that can sustain tender fruit and grape production, the Okanagan Valley and the Niagara Peninsula. These areas supply Canadians with a secure fruit supply at reasonable prices. Without it, unreliable foreign supplies would likely increase in price as there is no domestic competition.
• The Okanagan and Similkameen Valleys are found in arid to semi-arid climates. In these climates, evapotranspiration greatly exceeds precipitation inputs and farmers must supplement their crop's water needs through irrigation. Current data indicates that there is enough water in the Okanagan to meet demand. However, future increases in the size of human populations in this region will create competition for this water. The fruit industry could adjust by implementing technologies, like trickle irrigation systems, that save water. Trickle irrigation systems are currently employed in only 10 % of existing farms.
• Many orchards are in close proximity to residential complexes, schools and playgrounds resulting in human health dangers during spraying periods. The application of these chemicals may also be reducing numbers of individuals in certain sensitive nontarget species of amphibians, birds and insects.
• Because of the Okanagan Valley's topography and hydrology, a significant proportion of pesticide chemicals applied to fruit end up into the valley's lakes. Some of these chemical require up to 200 years for degradation into benign compounds. DDT which was used to fight coddling moth more than a decade ago is still found in small concentrations in Okanagan Lake fish.
• Applications of fertilizer are causing the eutrophication of aquatic systems of various size. Severe eutrophication can lead to blooms of algae, anoxic conditions, species die-offs and species change.
• Applications of nitrogen-based fertilizers and irrigation water on soils with low cation exchange capacitycan cause soil acidification. To reverse this process many farmers in the Thompson-Okanagan must lime (addition of calcium carbonate) their land to raise soil pH levels high enough for good plant growth.
• Poor farming techniques in many Thompson-Okanagan farms are leading to the erosion of topsoil. Erosion is especially problematic in the spring and fall months, when farm soils are devoid of vegetation.

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