Courseworks

Human Influences on the Environment

As the population of humans increases so must the cultivation of crops in order to feed them. Over the years different methods of farming have been used, many proving harmful to the environment, and changing the way the ecological system may have otherwise naturally developed. In this report my aim is to investigate the changes in farming and evaluate the effects on the environment.Before the 1950’s traditional farming techniques ruled the world of farming. These farming methods used processes such as:* Crop rotation: A simple definition of crop rotation is the planting of different crops in recurring succession in the same field. Research findings support the many benefits to good crop rotation systems, such as:� Maintains good soil physical condition and organic matter� Improves distribution of plant nutrients in the soil by varying the feeding range of roots� Improves fertility with legume nitrogen and, when using green manure crops, makes other plant nutrients more available� Fosters the most effective use of manure and fertilizer� Helps control weeds, some plant diseases and insect pests: this is because the lag phase which a pest has before becoming establishes will generally not be over before the new crop is introduced, and through changing the crop the pests source of nourishment will be gone, thus dying.� Reduces need for purchased herbicides and fertilizer� Can enhance soil moisture management� Promotes income diversity and stability through increased marketing options� Better allocates farmer’s labor and equipment usage through the year� Improves crop quality and yields by 10 – 15%� Provides low cost forages for livestock with return of manure on cropland� Reduces the cost of conservation compliance� Improves diversification and soil quality to reduce drought impact� Reduces soil erosion. Increases flora, fauna and wildlife diversity and numbers� Improves water quality through reduction in loss of agricultural chemical off-fieldThe introduction of modern farming techniques changed from that of crop rotation of mono-culture as this allows a high yield of one type of crop bringing in capital for landowners. However the growing of one crop year after year means that the soil lacks nutrients, therefore there has to be an introduction of fertilizers into the soil. Mono-culture farming also has other problems as they attract pests which mean the involvement of pesticides is necessary causing a whole range of other problems which will be addressed later in the report.* Hedgerows: hedgerows are described as a small bunch of bushes or small trees growing close together. Traditionally they were used as markers for the owners of land, separating fields and keeping livestock in place. They are beneficial because they act as a shelter for the field from damage caused by wind and rainfall. Hedgerows are also habitats for some animals and therefore allow a higher diversity of creatures in the field keeping the food chain in order, as well as the number of pests.However modern farming techniques have seen the depletion of hedgerows to create space for agricultural equipment and the extending of fields for monoculture. This has been done to allow a higher yield of crops for the increasing population but there have been implications which have come with this. The disadvantage of taking away hedgerows is that fields are more susceptible to soil erosion from wind and rain, soil erosion impairs the fertility of soil as nutrients are lost and therefore fertilizers must be introduced.* Traditional farming techniques also included the recycling of manure from livestock and growing legumes which build soil fertility because of there relationship with nitrogen fixing bacteria, therefore fixing nutrients back into the soil.As previously mentioned modern farming techniques rely heavily on the introduction of fertilizers into the soil in order to get a high yield of crops. In situations other than farming nutrients would be returned to the soil when the plant growing died, but the point of farming is to take out the crop whilst it is alive and therefore the nutrients are still inside it, and never returned to the soil.A fertile soil requires nitrogen, phosphorus and potassium, and once the crops have been harvested these nutrients must be replaced by either organic or in-organic fertilizers.Inorganic fertilizers contain quantities of nitrogen, phosphorus and potassium hydroxide which can be added to the soil or directly to the plants. Organic fertilizers consist of organic matter such as from manure or sewage sludge.The problem with the addition of these fertilizers occurs when the nutrients added in are lost from the agricultural fields. This can happen in a number of ways such as runoff, drainage or leaching.Leaching is the process by which soluble nutrients from topsoil percolates downward to become groundwater supplying water to streams, rivers and plants. It is the nitrogen and phosphorus which causes most problems as both are highly soluble and if get into streams and rivers etc cause the excessive growth of aquatic plants and lead to eutrophication.Eutrophication:Natural eutrophication is the process by which lakes etc gradually age and become more productive. It normally takes thousands of years to progress. However, humans through various cultural activities have accelerated the process by excessive amounts plant nutrients leaching into them. The nutrients cause excessive growth of algae which block out sunlight killing off other water plants creating a gap in the food chain and killing off many species. |Eventually the algae die and their decay leads to the depletion of oxygen killing off anything else left in the water allowing the lake to become stagnant.Biochemical oxygen demand:This is a measure of how much dissolved oxygen is being consumed as microbes break down organic matter. A high demand indicates that the levels of oxygen are falling, with potentially dangerous implications for a rivers biodiversity. High biochemical oxygen demand can be caused by high levels of organic pollution (caused usually by poorly treated wastewater) or by high nitrate levels which trigger aquatic plant growth.Organic fertilizers can also be used to replace nutrients which the soil has lost. This kind of fertilizer is applied by spreading manure or slurry over farmland. Although this method can also lead to eutrophication the chances of it happening are reduced because the manure/slurry is less soluble and effects water plants in a different way to inorganic fertilizer.Pesticides:The use of chemicals in order to control the amounts of pests is directly related to the modernized farming techniques employed by humans, through the destruction of hedgerows, crop-rotation and organic fertilizers.The most widely used pesticides are insecticides (those which kill insects), herbicides (those which kill weeds) and fungicides (those which kill fungus).An ideal pesticide would have many features such as being specific to the pest it was trying to control, non-toxic to other organisms, biodegradable and non-mobile. Unfortunately most pesticides are the complete opposite, and this is why they cause so many problems in the environment.One of the main problems is the lack of selectivity; this therefore affects whole food chains and can lead to the introduction of new pests because their predators are wiped out by the pesticide, the reduction of natural control can become a big problem.Also many pest species have developed a genetic resistance to pesticides after repeat exposure to them, this means that new pesticides are constantly required which can affect other species which many not be pests.Another problem is the mobility of a pesticide, as most come in liquid form they are easily washed away from the area of placement and can get into a food chain via this movement.Persistence: This is defined as the lasting power of a pesticide. Most can be broken down by micro-organisms (considered by most to be the safest way), chemicals (this is generally on partial degration and therefore not ideal) or sunlight (which can again lead to partial degration and can take a long time).Some pesticides are extremely stable and can take many years to be broken down, giving them time to accumulate inside organisms and food chains. Pesticides tends to be fat-soluble rather that water soluble therefore once inside an organism it cannot be excreted and is stored in fatty tissues, a process known as bioaccumulation.Biomagnification leads to bioaccumulation; this is what happens as the pesticide passes from one trophic level to another. For example is a pesticide leached into a river and some organisms (such as a water flea) accumulated some on the next trophic level a organism (like a fish) would need to eat a large amount of the fleas to suit its own energy requirements thus taking and accumulating pesticides from a number of fleas. As we moved up the trophic levels of the food chain it would become apparent that the predator at the top would have accumulated the pesticides form all of the species below and would more than likely die out.Ways in which we can help the situation:It has become obvious that human farming and more specifically the technology associated with it has had a major effect on food chains, ecology and the environment. And as the population of humans increases it is easy to assume that the effects will heighten because there will be a higher demand for crops, leading to an increase in farming and an increase in the technology used to make it easier to produce the high yields required. But if we continue farming in the way that we have been we will end up polluting ourselves and destroying even more wildlife so it is important for new methods to be thought up and new technology to be employed.There are a number of ways in which farmers can help to decrease the amount of fertilizers and pesticides leaching into water supplies, such as:* Planting hedgerows* Biological control (introduction of natural predators to take care of pests rather than chemicals being used)* When planting crops on slopes plant woodlands as the trees will shelter the soil from the rain stopping as much water containing pesticides/fertilizers leaching. Also the roots will hold the top soil together better helping with erosion.* Use of organic fertilizer* Ploughing along contours (preventing soil erosion)* Crop rotation farming

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