2. Agriculture We will examine three aspects of modern agricultural practice that pose a threat to biodiversity. (a) Monoculture (b) Overuse of herbicides and pesticides (c) Overuse of fertilisers
(a) Monoculture Monoculture is an agricultural practice where only one species is produced. For example Fig. 11 shows a field where only cabbages are grown. Monoculture allows us to produce large amounts of food at a lower cost because the entire crop can be treated with the same type of fertilisers and pesticides and can be harvested at the same time.
Fig. 11 In a monoculture land is only used for one species.
Monoculture threatens biodiversity because: Other plants are prevented from growing, therefore reducing the biodiversity of plants. The animals that relied on those other plants for food or shelter can no longer live in that environment. This reduces the biodiversity of animals.
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(b) Overuse of herbicides and pesticides Herbicides and pesticides kill organisms that damage and reduce food crops. This reduces competition between crops and other plants, and between crops and insects.
Overuse of herbicides and pesticides threatens biodiversity because: They reduce the variety of species found in the area where they are used. They can stay in the environment for a long time and can be passed to other organisms through the food chain.
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Fig. 12 Herbicides and pesticides are sprayed to kill organisms that damage crops.
(c) Overuse of fertilisers Fertilisers are substances that are applied to add nutrients to soil. They can be natural, like slurry, or they can be artificial. Plants absorb nutrients from the soil through their roots. Using fertilisers increases the growth of plants and therefore the amount of food that can be produced from the land.
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Overuse of fertilisers is a threat to freshwater biodiversity because: Fertilisers can seep into streams, rivers and lakes. This can cause a lot of algae to grow in the water. The algae blocks light and this reduces the amount of light available to water plants for photosynthesis.
