Biodiversity and the effect of human interaction on ecosystems

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수업 노트

What Biodiversity Is and Why It Matters

Biodiversity is the variety of all the different species of organisms on Earth, or within a particular ecosystem.
A highly biodiverse ecosystem is stable because of the large number of interdependent species it contains.
Species depend on each other for food, shelter (such as birds nesting in trees) and maintenance of the physical environment (such as tree roots holding soil together).
High biodiversity reduces the dependence of one species on another, so if one population is lost, others can still survive on alternative food sources.
A large number of interconnected food chains is most likely to produce a biodiverse ecosystem.
The future of the human species relies on maintaining biodiversity: we depend on photosynthetic organisms for oxygen, pollinators such as bees for food crops, and plants for medicines.

Human Population Growth and Waste

The human population has grown exponentially over the last 150 years.
Growth is driven by improved technology giving an abundance of food (raising the birth rate) and improved medicine, hygiene and health care (lowering the death rate).
A rising population and an increasing standard of living mean more resources are used and more waste is produced.
Unless waste and chemical materials are properly handled, pollution will continue to be created.
Pollution kills plants and animals, which reduces biodiversity.

Types of Pollution

Water pollution comes from sewage, fertiliser or toxic chemicals.
Air pollution comes from smoke and acidic gases, such as sulfur dioxide released by burning fossil fuels.
Land pollution comes from landfill and from toxic chemicals.
Pollutants can build up in organisms: bioaccumulation is the build-up of a substance within one organism, while biomagnification is the increase in concentration of a dangerous compound at successive trophic levels.
Air pollution such as sulfur dioxide can lead to acid rain, which damages habitats.

Eutrophication

Runoff of fertiliser from farmland enters water and causes increased growth of algae and water plants.
The resulting algal bloom blocks sunlight, so water plants on the bottom die, and the algae die too when competition for nutrients becomes too intense.
As plants and algae die in greater numbers, decomposing bacteria increase and use up the dissolved oxygen while respiring aerobically.
With less dissolved oxygen, aquatic organisms such as fish and insects may be unable to survive, reducing biodiversity.
Sewage and fertiliser runoff both end with a decrease in dissolved oxygen, but only fertiliser runoff causes algal blooms.
Indicator species can reveal pollution levels: stonefly larvae and freshwater shrimps indicate clean water, while blood worms and sludgeworms indicate very high water pollution.
Lichen and blackspot fungus are sensitive to sulfur dioxide, so a high abundance of bushy lichen indicates very clean air.

Sequence of events causing eutrophication

Land Use and Peat Bogs

An increasing human population needs more land for building, quarrying, farming and dumping waste, destroying habitats such as rainforests and woodlands.
This reduces biodiversity and interrupts food chains and webs, so more species may die because their prey is gone.
Peat bogs are waterlogged, acidic areas where plants do not fully decay due to a lack of oxygen, so partly decomposed plant matter accumulates as peat.
Carbon that would have been released as carbon dioxide is instead stored in the peat.
Peat bogs are drained for farming, dried and burned as fuel, or used to produce compost for gardens and farms.
Burning peat releases carbon dioxide into the atmosphere, contributing to global warming, and the loss of peat bog habitat reduces biodiversity.
Peat bogs form so slowly that peat is effectively a non-renewable resource and is being used unsustainably.

Deforestation

Deforestation is the clearing of trees, usually on a large scale.
It can be sustainable if trees are replanted, but unsustainable deforestation is occurring where forests are cut down faster than they can regenerate.
Large-scale deforestation in tropical areas occurs to provide land for cattle and rice fields and to grow crops for biofuels.
Deforestation is a severe form of habitat destruction, causing extinction of species, loss of soil, flooding and an increase of carbon dioxide in the atmosphere.
Removing trees means less carbon dioxide is removed from the air by photosynthesis, and burning or decaying vegetation releases carbon dioxide.
Reforestation — replanting large areas with a variety of tree species — helps rebuild biodiversity and maintain the global carbon balance.

Global Warming

Greenhouse gases absorb infrared radiation from the Sun so heat remains trapped in the Earth's atmosphere.
The most important greenhouse gases include water vapour, carbon dioxide, methane, nitrous oxides and CFCs.
Carbon dioxide is produced by the combustion of fossil fuels; methane is released by cattle digesting grass and by rice paddy fields.
Rising levels of greenhouse gases cause an enhanced greenhouse effect, raising the Earth's average temperature beyond normal — this is global warming.
Consequences include melting polar ice caps, rising sea levels, flooding, coral bleaching, extreme weather such as super storms and droughts, habitat loss, and decreased biodiversity.
Global warming can also increase the migration of species to new places, including the spread of pests and disease.
There is scientific consensus that global warming is happening and that human activities are largely responsible, based on systematic reviews of thousands of peer-reviewed papers.

Maintaining Biodiversity

Humans can interact positively with ecosystems through conservation programmes.
Protected areas are habitats that are not allowed to be interfered with, for example no building work is allowed.
Breeding programmes selectively breed organisms, often in zoos, to increase population numbers of endangered species.
Seed banks store seeds of plant species for many years under the right conditions to future-proof the species.
Reducing deforestation and carbon dioxide emissions, and recycling resources rather than dumping waste in landfill, also help.
Field margins and hedgerows can be reintroduced in agricultural areas where farmers grow only one type of crop, providing habitats and increasing biodiversity.
Maintaining biodiversity protects the human food supply, sources of medicines, jobs in conservation and ecotourism, and cultural traditions linked to nature.
Peatlands and wetlands store large amounts of carbon, so protecting them helps reduce carbon dioxide released into the atmosphere.

Conflicting Pressures on Biodiversity

Protecting biodiversity can be very expensive; for example, land used for field margins could otherwise grow crops, so governments may pay farmers a subsidy.
It also costs money to check that programmes designed to maintain biodiversity are actually being followed.
Land protected for biodiversity could instead be used for farming, causing conflict where there are food shortages.
Organisms seen as a threat by farmers, such as locusts and wolves, may be killed to protect crops and livestock, which can negatively affect food chains.
Increasing amounts of land are needed for housing and new agricultural land as the human population grows, so undisturbed habitats with high biodiversity are increasingly used for development.

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연습 문제

무료 미리 보기 — 61개 중 8개 문제. 가입하면 전부 볼 수 있어요.

1.Biodiversity means the total number of individual organisms in an ecosystem, rather than the variety of species.
Easy
True or false?
2.Which of the following best defines biodiversity?
Easy
- AThe variety of different species within an ecosystem or on Earth
- BThe total number of organisms in a habitat
- CThe number of individuals of a single species
- DThe total biomass of all organisms in an ecosystem
3.Which of the following human activities reduce biodiversity? (Select all that apply)
Medium
- ADeforestation
- BProducing waste
- CGlobal warming
- DPlanting a variety of tree species
- EUsing field margins
4.Which of the following is not a consequence of deforestation?
Medium
- AIncreased biodiversity
- BExtinction of species
- CLoss of soil
- DIncrease of carbon dioxide in the atmosphere
5.Eutrophication is caused by increased growth of algae due to fertiliser runoff, which eventually leads to decreased oxygen levels in water.
Easy
True or false?
6.What is the first step in eutrophication?
Medium
- ARunoff of fertiliser into water
- BDeath of aquatic organisms
- CDecomposition of algae by bacteria
- DIncrease in dissolved oxygen
7.The presence of stonefly larvae in a stream indicates that the water is polluted.
Easy
True or false?
8.Which organism is an indicator of very high water pollution?
Easy
- ABlood worms
- BStonefly larvae
- CFreshwater shrimps
- DBushy lichen

더 많은 문제

9.Which of the following is not a consequence of global warming?
Medium
- AIncrease in fossil fuel regeneration
- BRising sea levels
- CChanges in migration patterns of birds
- DHabitat loss for certain animals
10.Which of the following are benefits of maintaining biodiversity? (Select all that apply)
Medium
- AHuman food supply
- BMedicines from plants
- CJobs in conservation and ecotourism
- DIncreased global warming
- EClimate change
11.Which of the following is a method of conserving species?
Medium
- ABreeding programmes
- BDeforestation
- CPeat bog destruction
- DIncreasing waste production
12.Which of the following are consequences of deforestation? (Select all that apply)
Medium
- AExtinction of species
- BLoss of soil
- CFlooding
- DIncrease of carbon dioxide in the atmosphere
- EIncreased stability of food webs
13.Which of A - D is most likely to lead to a biodiverse ecosystem?
Medium
- AA large number of unconnected food chains
- BA large number of interconnected food chains
- CA small number of unconnected food chains
- DA small number of interconnected food chains
14.Which of the factors A - D is not likely to have a negative impact on biodiversity of a marine ecosystem?
Medium
- AHuman introduction of more lobsters into the area
- BGlobal warming
- CSewage ingress into the sea
- DImposition of fishing quotas
15.Which of the following factors would lead to an increased amount of human waste being produced? (Select all that apply)
Medium
- AIncreasing standard of living
- BIncreasing population
- CIncreasing life expectancy
- DDecreasing standard of living
- EDecreasing population
16.Draw a straight line between each pollutant and the effect that it creates.
Medium
- Sulphur dioxide released from power stations
- Fertiliser runoff into a lake
- Raw sewage released into a river
- Non-biodegradable pesticide in a food chain
- Acid rain
- Algal bloom blocking sunlight
- Increase in decomposing bacteria using up dissolved oxygen
- Biomagnification at successive trophic levels
17.Which of A - D is not a possible consequence of global warming?
Medium
- AChanges in migration patterns of birds
- BSea level rise
- CIncrease in fossil fuel regeneration
- DHabitat loss for certain animals
18.Place the stages of eutrophication in the correct order, starting with the first event.
Medium
- Fertiliser runoff enters the water
- Algae and water plants grow rapidly, forming an algal bloom
- Sunlight is blocked, so water plants and algae die
- Decomposing bacteria increase and use up dissolved oxygen
- Fish and insects cannot survive due to lack of oxygen
19.The presence of blood worms and sludgeworms in a body of water indicates a very high level of water pollution.
Easy
True or false?
20.Which of the following statements about lichens as indicator species are correct? (Select all that apply)
Medium
- ALichens are highly sensitive to sulfur dioxide concentrations
- BA high abundance of bushy lichen indicates very clean air
- CLichens grow best in areas with high sulfur dioxide levels
- DLichens can be used to monitor air pollution on trees and buildings
- ECrusty lichen need cleaner air than bushy lichen
21.Which of A - D is the best definition of biodiversity?
Medium
- AThe total number of individual organisms in an ecosystem
- BThe variety of different species of organisms on Earth, or within an ecosystem
- CThe number of food chains in a habitat
- DThe total mass of living material in an ecosystem
22.Which of A - D is not a method used to conserve species?
Medium
- AProtected areas where building is not allowed
- BBreeding programmes in zoos
- CSeed banks storing seeds for many years
- DIncreasing the use of peat-based compost in gardens
23.Arrange the following steps to show how human population growth leads to increased pollution.
Medium
- Human population grows exponentially
- More resources are used to sustain the population
- More waste is produced
- Waste is not properly handled
- Pollution is created
24.Which of the following are reasons why maintaining a high level of biodiversity is important? (Select all that apply)
Hard
- AIt helps to maintain the stability of ecosystems
- BSome medicines are extracted from plants that may be at risk of extinction
- CIt provides jobs through conservation and ecotourism
- DIt guarantees that no species will ever become extinct
- EPeatlands and wetlands store carbon, helping to reduce carbon dioxide release
25.Match each human activity with its effect on biodiversity.
Medium
- Deforestation
- Peat bog destruction
- Introduction of a non-indigenous species
- Increased greenhouse gas emissions
- Habitat loss and increased atmospheric carbon dioxide
- Release of stored carbon dioxide and loss of habitat
- Competition with native species and spread of disease
- Global warming causing coral bleaching and habitat loss
26.The destruction of peat bogs releases methane into the atmosphere.
Medium
True or false?
27.Which of A - D best explains why plant material decays so slowly in a peat bog?
Medium
- AThe conditions are waterlogged and acidic, so there is little oxygen
- BThe conditions are dry and alkaline, so decomposers thrive
- CThe temperature is too high for decomposers
- DThere are too many decomposing bacteria present
28.Peat is effectively a non-renewable energy source because peat bogs take so long to form.
Medium
True or false?
29.A lake receives runoff containing fertiliser. Which sequence of events correctly describes the resulting eutrophication?
Medium
- AAlgal bloom → light blocked → water plants die → decomposers increase → dissolved oxygen falls
- BDecomposers increase → dissolved oxygen falls → algal bloom → light blocked → water plants die
- CDissolved oxygen falls → algal bloom → decomposers increase → light blocked → water plants die
- DLight blocked → algal bloom → dissolved oxygen falls → decomposers increase → water plants die
30.A stream is sampled and found to contain stonefly larvae, freshwater shrimps and blood worms. Which statements about this sample are correct? (Select all that apply)
Hard
- AThe presence of stonefly larvae suggests the water is clean with high oxygen levels
- BThe presence of blood worms suggests a very high level of water pollution
- CThe sample shows the water is completely unpolluted everywhere
- DIndicator species can give accurate numerical values for the exact pollution level
- EThe presence of freshwater shrimps suggests the water is not heavily polluted
31.A high abundance of bushy lichen on trees indicates very clean air.
Easy
True or false?
32.Match each human activity to its effect on biodiversity.
Medium
- Burning peat as fuel
- Introducing grey squirrels to the UK
- Using fertiliser on farmland next to a river
- Clearing rainforest for cattle grazing
- Releases carbon dioxide and destroys a habitat
- Outcompetes red squirrels and spreads disease
- Causes eutrophication, reducing dissolved oxygen
- Destroys habitats and reduces species variety
33.A conservation charity wants to protect a rare orchid species. Which method would be most effective for long-term protection of the species' genetic material?
Medium
- AStoring seeds in a seed bank
- BBuilding a new road through the habitat
- CIncreasing the use of pesticides on nearby farms
- DIntroducing a non-indigenous predator
34.A student uses a dissolved oxygen meter to measure oxygen concentration at four points along a river. The results are: point A 9.8 mg/dm³, point B 7.2 mg/dm³, point C 4.1 mg/dm³, point D 1.3 mg/dm³. At which point would you expect to find the greatest abundance of blood worms and sludgeworms?
Medium
- APoint A
- BPoint B
- CPoint C
- DPoint D
35.A student wants to compare air pollution at two sites. At site 1 there is a high abundance of bushy lichen. At site 2 there is only crusty lichen. Which conclusion is best supported by these observations?
Medium
- ASite 1 has a higher sulfur dioxide concentration than site 2
- BSite 2 has cleaner air than site 1
- CSite 1 has cleaner air than site 2
- DBoth sites have identical air quality
36.A scientist wants to obtain accurate numerical data on how water pollution changes over several months in a river. Which methods would be most suitable? (Select all that apply)
Hard
- ARecording the presence or absence of stonefly larvae
- BUsing a dissolved oxygen meter to measure oxygen concentration
- CPerforming chemical tests to measure dissolved oxygen concentration
- DCounting the number of lichen species on nearby trees
- ENoting whether blood worms are present
37.Using indicator species is a cost-effective method of assessing pollution, but it cannot give accurate numerical values for how much pollution is present.
Easy
True or false?
38.In a fish farm, fish are grouped according to their age and size. What is the main reason for this?
Medium
- ATo prevent interspecific predation
- BTo limit intraspecific predation
- CTo increase the spread of disease
- DTo encourage the growth of algae
39.Which of the following are methods used in fish farms to maximise yield? (Select all that apply)
Hard
- ASelective breeding for fast growth
- BFeeding high-protein fish pellets
- CAllowing fish to compete for food naturally
- DMonitoring water pH and temperature
- EUsing antibiotics to prevent disease
40.Which term describes the variety of all the different species of organisms on Earth, or within an ecosystem?
Easy
- AEcosystem
- BBiodiversity
- CPopulation
- DCommunity
41.Name the term for the variety of different species of organisms on Earth, or within an ecosystem.
Easy
42.Pesticide levels in the water of a lake were measured at 877 parts per billion. The same pesticide was measured in the gills of a fish living in that lake and showed biomagnification by a factor of 9 750 000 times. Calculate the concentration of the pesticide in the fish's gills, in parts per billion. Give your answer in standard form.
Hard
43.Complete the sentence about the importance of biodiversity.
Medium
A high biodiversity ensures the ____ of ecosystems by reducing the dependence of one species on another for food, shelter and the maintenance of the physical environment.
44.Name three indicator species or groups used to assess water pollution.
Medium
Indicator species for water pollution include ____, ____, and ____.
45.Pesticide levels in the water of a lake were measured at 877 parts per billion. The same pesticide was measured in the gills of a fish living in that lake and showed biomagnification by a factor of 9.75 million (9 750 000) times. Calculate the concentration of the pesticide in the fish's gills. Give your answer in standard form, in parts per billion.
Medium
46.Globally, 88 000 km² of natural forest is lost every year. A football pitch has an area of 7 140 m². Calculate the time taken, at the current rate of deforestation, for a football pitch-sized piece of land to be deforested. Give your answer to the nearest whole second. (1 km² = 1 000 000 m²)
Hard
47.Complete the sentence about global warming and the greenhouse effect using the correct terms.
Medium
Greenhouse gases absorb ____ radiation emitted from the Earth's surface, and increasing levels of these gases cause the Earth's average ____ to rise.
48.Name the two gases that are the main contributors to the enhanced greenhouse effect from human activities.
Medium
The two main greenhouse gases increased by human activity are ____ and ____.
49.A lake contains pesticide at a concentration of 877 parts per billion (ppb). In the gills of a fish from the lake, the pesticide concentration is 9.75 million times greater. Calculate the pesticide concentration in the fish's gills, in parts per billion. Give your answer in standard form.
Medium
50.Complete the sentence about the effect of an enhanced greenhouse effect.
Medium
Greenhouse gases absorb ____ radiation, so as their concentration increases the Earth's average ____ rises, causing global warming.
51.Name the process by which a non-indigenous species outcompetes a native species for food, water or space, often leading to the native species being eradicated.
Easy
52.Complete the sentence about biomagnification.
Medium
Biomagnification is the increase in concentration of a substance at each successive ____ level in a food chain.
53.Explain how deforestation impacts the concentration of carbon dioxide in the atmosphere.
Hard
54.Describe how the removal of woodland areas can have a bad effect on other organisms.
Medium
55.Question 2d) gives an example of biomagnification, in which the level of a dangerous compound gets higher at successive trophic levels. Explain how biomagnification differs from bioaccumulation.
Hard
56.Describe two ways in which the negative effects of humans on biodiversity and the ecosystem can be reduced.
Hard
57.Suggest why the destruction of peat bogs is controversial.
Hard
58.Pesticide levels in the water of a lake were measured at 877 parts per billion. The same pesticide was measured in the gills of a fish living in that lake and showed biomagnification by a factor of 9 750 000 times. Calculate the concentration of the pesticide in the fish's gills, in parts per billion. Give your answer in standard form.
Hard
- A8550000000 parts per billion
- B10260000000 parts per billion
- C9405000000 parts per billion
- D7695000000 parts per billion
59.Pesticide levels in the water of a lake were measured at 877 parts per billion. The same pesticide was measured in the gills of a fish living in that lake and showed biomagnification by a factor of 9.75 million (9 750 000) times. Calculate the concentration of the pesticide in the fish's gills. Give your answer in standard form, in parts per billion.
Medium
- A9405000000 parts per billion
- B7695000000 parts per billion
- C8550000000 parts per billion
- D10260000000 parts per billion
60.Globally, 88 000 km² of natural forest is lost every year. A football pitch has an area of 7 140 m². Calculate the time taken, at the current rate of deforestation, for a football pitch-sized piece of land to be deforested. Give your answer to the nearest whole second. (1 km² = 1 000 000 m²)
Hard
- A2817 seconds
- B2305 seconds
- C3073 seconds
- D2561 seconds
61.A lake contains pesticide at a concentration of 877 parts per billion (ppb). In the gills of a fish from the lake, the pesticide concentration is 9.75 million times greater. Calculate the pesticide concentration in the fish's gills, in parts per billion. Give your answer in standard form.
Medium
- A9405825000 ppb
- B10260900000 ppb
- C7695675000 ppb
- D8550750000 ppb

플래시카드

What is biodiversity?

The variety of all the different species of organisms on Earth, or within an ecosystem.

Why does a high level of biodiversity make an ecosystem stable?

It reduces the dependence of one species on another for food, shelter and the maintenance of the physical environment.

Give three things that different species depend on each other for.

Food, shelter (such as birds nesting in trees) and maintenance of the physical environment (such as tree roots stabilising soil).

In a food web, why might the loss of one prey species not wipe out a predator?

If the predator has other prey species to feed on, its population may decrease but it will not be wiped out.

Why does the future of the human species rely on maintaining biodiversity?

Humans depend on other species: photosynthetic organisms produce oxygen, pollinators such as bees pollinate food crops, and many plants provide medicines.

Give two reasons why the human population has grown exponentially over the last 150 years.

Improved technology has led to an abundance of food, increasing the birth rate, and improved medicine, hygiene and health care have decreased the death rate.

Why does a rising human population and standard of living increase pollution?

More resources are used to sustain the population, so more waste is produced, and unless waste and chemical materials are handled properly, pollution is created.

State three places where pollution can occur and give an example of each.

In water (sewage, fertiliser or toxic chemicals), in air (smoke and acidic gases) and on land (landfill and toxic chemicals).

How does pollution reduce biodiversity?

Pollution kills plants and animals, which reduces the variety of species living in the affected habitat.

Describe the sequence of events that causes eutrophication.

Fertiliser runoff enters water and causes an algal bloom; the algae block sunlight so water plants die, and decomposing bacteria increase and use up dissolved oxygen, so aquatic animals such as fish and insects cannot survive.

How does sewage pollution reduce oxygen levels in water?

Sewage contains nitrates that cause microorganisms to increase in number; as they respire they use up the dissolved oxygen in the water.

What is the difference between bioaccumulation and biomagnification?

Bioaccumulation is the build-up of a substance within a single organism over its lifetime, while biomagnification is the increasing concentration of that substance at each successive trophic level of a food chain.

Give four ways humans reduce the land available for other animals and plants.

Building, quarrying, farming and dumping waste.

What is a peat bog and how is peat formed?

A waterlogged, acidic area where plants do not fully decay due to a lack of oxygen, so partly decomposed plant matter accumulates over very long periods to form peat.

Why is destroying peat bogs a problem for the atmosphere?

The carbon stored in the peat is released as carbon dioxide when the peat decays or is burned, contributing to global warming.

Why is peat considered a non-renewable energy source?

Peat bogs take so long to form that peat is being used up much faster than it can be replaced.

Give two reasons why peat bogs are being destroyed.

They are drained for farming, and peat is dried and used as a fuel or to produce compost for gardens and farms.

What is deforestation?

The clearing of trees, usually on a large scale.

When is deforestation sustainable?

When the trees that are cut down are replaced by replanting, so the forest can regenerate.

Give two reasons why large-scale deforestation occurs in tropical areas.

To provide more land for farming (such as cattle and rice fields) and to grow crops from which ethanol-based biofuels can be produced.

State four undesirable effects of deforestation.

Extinction of species, loss of soil, flooding and an increase in carbon dioxide in the atmosphere.

How does deforestation increase carbon dioxide in the atmosphere?

Trees remove carbon dioxide from the atmosphere for photosynthesis, so fewer trees means less carbon dioxide is taken in; burning the cleared trees also releases carbon dioxide.

What is a greenhouse gas?

A gas that absorbs infrared radiation from the Sun so that heat remains trapped in the Earth's atmosphere.

Name the most important greenhouse gases.

Water vapour, carbon dioxide, methane, nitrous oxides and CFCs.

How do human activities increase carbon dioxide and methane levels?

Carbon dioxide is produced by burning fossil fuels, and methane is released by cattle digesting grass and by rice paddy fields.

Explain how the enhanced greenhouse effect causes global warming.

As levels of greenhouse gases rise, more heat bounced back from the Earth's surface is absorbed and trapped in the atmosphere, so the Earth's average temperature rises beyond normal.

Give three consequences of global warming.

Rising ocean temperatures causing melting polar ice caps, rising sea levels and flooding; more extreme weather such as super storms and droughts; and habitat loss that disrupts food chains and increases extinction rates.

Why is there scientific consensus that human activity is causing global warming?

It is based on systematic reviews of thousands of peer-reviewed scientific research papers, which check each other's work to ensure findings are valid.

Why is it difficult for scientists to predict the exact consequences of global warming?

The evidence is uncertain and incomplete because the climate is a complex system, so scientists can make good predictions but cannot say for certain what will happen.

Give three methods used to conserve species under threat.

Protected or conservation areas where land cannot be interfered with, breeding programmes that selectively breed organisms to increase population numbers, and seed banks that store seeds for many years.

How does reforestation help maintain biodiversity?

Replanting large areas of forest with a variety of tree species rebuilds the biodiversity of cleared areas, provides habitats and helps maintain the global carbon balance by removing carbon dioxide for photosynthesis.

What is a field margin and how does it increase biodiversity?

A strip of land around the edge of a field left to grow wild plants; it provides habitats and food for a wider variety of species than a single crop alone.

Give two conflicting pressures on maintaining biodiversity.

The cost of conservation programmes (such as paying farmers subsidies for land used as field margins) and protecting food security, since protected land could instead be used for farming.

Why can protecting biodiversity be expensive?

Land used for conservation, such as field margins, cannot be used to grow and sell crops, so governments may pay subsidies, and it also costs money to check that programmes are being followed.

Give two ways the negative effects of humans on ecosystems can be reduced.

Recycling resources rather than dumping waste in landfill, and reducing deforestation and carbon dioxide emissions.

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