Human impacts on biodiversity

In a nutshell

Human activities can have both positive and negative impacts on biodiversity. Biodiversity is important for ecosystems to maintain stability. Negative human activities include using fertilisers, fish farms, waste production, deforestation, destroying peat bogs, monocultures and hunting.

Biodiversity

Definition

Biodiversity is the variety of living organisms in an ecosystem.

Having high biodiversity can mean an ecosystem is more stable. For the human species to survive, it is important that a good level of biodiversity is maintained. Human interactions within ecosystems can affect biodiversity. Sometimes they can be positive and sometimes they are negative.

Negative human impacts on biodiversity

Eutrophication

Nitrates are put onto fields as fertilisers. If too much fertiliser is applied and it rains, nitrates can leach into rivers and lakes. This causes an excess of nutrients in water or eutrophication. This can lead to the death of many species in the water which will reduce biodiversity.

Biology; Ecosystems and material cycles; KS4 Year 10; Human impacts on biodiversity

1.	Fertilisers leach into water and add excess nitrates.
2.	The excess nitrates cause the rapid growth of algae.
3.	They cause a bloom (A) on the surface of the water and block out the light.
4.	Plants underneath the algal bloom cannot photosynthesise due to the lack of light. They start to die and decompose. Microorganisms (B) that feed on decomposing plants (C) have more food and increase in numbers using up oxygen in the water as they do so.
5.	Organisms such as fish that need oxygen for aerobic respiration die.

Fish farms

Fish farms in areas of open water can reduce biodiversity in the surrounding areas.

1.	Food is added to the nets to feed fish, this produces waste. Both the food and waste can leak into open water which causes eutrophication and death of wild species.
2.	Fish farms in open water can act as breeding grounds for large numbers of parasites. These parasites can get out of the farm and infect wild animals.
3.	Predators can be attracted to fishing nets and become trapped in them. This may cause their death.
4.	Farmed fish can sometimes escape into the wild which can cause issues for wild populations of indigenous species.

Fish can also be farmed in large tanks, which tend to have low biodiversity as they only contain one species of fish. The tanks are also kept free of plants and predators. Parasites and other pathogens are killed.

Waste production

As humans make more things, we produce more waste and waste chemicals. This waste can cause harmful pollution that kills plants and animals if it is not handled properly. Pollution can affect water, land and air.

Water	Sewage and toxic chemicals from industry can pollute lakes, rivers and oceans. Fertilisers cause eutrophication. This will affect the plants and animals that rely on these water sources for survival.
Land	Toxic chemicals such as herbicides and insecticides are used for farming. Household waste is dumped at landfill sites.
Air	Smoke and acidic gases can pollute the air if they are released into the atmosphere. Sulphur dioxide can cause acid rain.

Deforestation

Deforestation is the cutting down of trees. It is done to clear lands for farming to provide more food and grow crops for biofuels. It can cause serious problems when done on a large scale.

Examples

Consequence	Explanation
*Less carbon dioxide is taken in*	Trees take in carbon dioxide from the atmosphere during photosynthesis, cutting down trees means less carbon dioxide is removed from the atmosphere.
*More carbon dioxide is released*	Carbon dioxide is released when trees are burnt to clear land. Microorganisms that fed on dead wood release carbon dioxide through respiration.
*Less biodiversity*	Habitats like forests contain many species of plants and animals, they have high biodiversity. When forests are destroyed, many species become extinct.

Destroying peat bogs

Bogs are areas of land that are acidic and waterlogged. Plants that live in bogs don't fully decay when they die, these decaying plants build up and form peat. Carbon in the plants is therefore stored in peat. Peat bogs can be drained so peat can be sold to gardeners as compost. When the peat bog is drained, microorganisms that break peat down release carbon dioxide as they respire. Peat can also be sold as a fuel, this releases carbon dioxide as the peat is burned. Destroying bogs reduces the area of the habitat which reduces biodiversity.

Monocultures

This is when areas of land are used to grow a single crop. This is an efficient way to grow crops for farmers but can lead to a reduction in biodiversity. This is because habitats are cleared to make way for the large fields that are needed.

Example

In Africa, large areas of land are used for palm oil plantations.

Hunting

Some animal species are hunted and this reduces their numbers. This can result in their endangerment or extinction. This reduces biodiversity.

Example

Species of rhino are hunted for their horns and this means they are endangered.

Non-indigenous species

Definition

A species that doesn't naturally occur in an area.

Non-indigenous species can be introduced naturally or unintentionally. The introduction of non-indigenous species may cause problems for indigenous species. Non-indigenous species compete with indigenous species for resources and sometimes they're better at getting these resources, this means they out-compete the indigenous species. This decreases their number and eventually they die out which reduces biodiversity.

Example

The cane toad from Hawaii was introduced into Australia in the $1930s$ , it carried many diseases that indigenous species had no resistance to.

Non-indigenous species can also bring new diseases that infect and kill lots of indigenous species. This once again reduces biodiversity.

Biology; Ecosystems and material cycles; KS4 Year 10; Human impacts on biodiversity