18.3. Threats and Reasons to Maintain Biodiversity Flashcards
1
Q
5 major threats to biodiversity
A
1) habitat loss and the degradation of the environment
2) climate change
3) excessive use of fertilisers and industrial and domestic forms of pollution
4) the overexploitation and unsustainable use of resources
5) the effects of invasive alien species on native species, especially endemics.
2
Q
Habitat Loss
A
- The destruction of the natural environment leads to habitat loss
- Deforestation has had a devastating effect on the biodiversity of some countries
- The clearing of land for agriculture, housing, transport, leisure facilities and industry removes vegetation.
- Consequently, many species of plant and animal either lose their habitats completely or their habitats become divided into small areas; this is known as habitat fragmentation. Most at risk of extinction are endemic species on small islands
- Deforestation can lead to severe degradation as a result of soil erosion once the vegetation is removed
3
Q
Overexploitation of Resources
A
- Although agriculture provides most of our food, we still rely on taking wild fish from the environment.
- It is very difficult to know whether fish stocks are sustainable, but the history of the fishing industry suggests that many species have been driven to near extinction by overfishing
- The response to the steep decrease in large, predatory species is to fish further down the food chain taking smaller fish that other animals, such as marine mammals and sea birds, depend upon.
- Fishing is just one example of the overexploitation of resources
- Another example is the removal by logging companies of valuable trees, such as teak and mahogany, at a rate faster than they can regenerate
4
Q
Loss of a species in a community
A
- Can have devastating effects on the rest of the community
- Organisms like the sea otter that play a central role in an ecosystem are known as keystone species
5
Q
Domestic waste as a form of pollutant
A
- In many countries, industrial and domestic waste is processed to reduce its impact on the environment.
- For example, sewage is treated before it reaches aquatic ecosystems, such as rivers and the sea.
- Much toxic industrial waste is collected and disposed of so that it cannot leak into the environment.
- However, this does not happen everywhere with the result that many ecosystems are polluted, often with substances that animals’ bodies are unable to metabolise or excrete
- Polychlorinated biphenyls (PCBs) were used in various manufacturing processes.
- Waste from factories used to flow directly into rivers without any form of treatment.
- Even though PCBs are no longer used, the substance persists in the environment and has entered food chains.
- Among its effects are weakening of immune systems and reduction in fertility in birds and mammals.
- PCBs were one of the factors contributing to the deaths of seals in the North Sea from a viral infection.
6
Q
Plastics as a form of pollution
A
- Non-biodegradable plastic is a major marine pollutant. - Animals, such as dolphins and turtles, get caught in discarded fishing nets and die.
- Turtles eat plastic bags mistaking them for jellyfish
7
Q
Fertilisers as a form of pollution
A
- Much of the world’s farmland is in low-lying land near coasts.
- Fertilisers that have not been absorbed by crop plants drain into rivers and then into the sea.
- The extra nutrients that become available to river and marine ecosystems cause growth of producers, such as algae
- This often occurs faster than herbivorous organisms, such as fish, can feed on them to keep their growth under control.
- Many of these algae produce toxic substances and their growth often unbalances food webs.
- Excess growth of algae has catastrophic effects on coral reefs and hugely reduces biodiversity
8
Q
Air Pollution
A
- Leads to problems for aquatic and terrestrial ecosystems
- The combustion of fuel with a high sulfur content, such as coal, leads to high concentrations of sulfur dioxide in the atmosphere.
- This reacts with water vapour to fall as acid rain.
- Acid rain has destroyed vegetation and led to the acidification of aquatic ecosystems in parts of the world downwind of highly industrialised areas.
- Few animals can survive and/or breed in waters of low pH, so the biodiversity has decreased markedly.
- Increased emission of greenhouse gases such as methane and CO2 has lead to global warming Build up of greenhouse gases → climate change
- Global warming is likely to produce changes in the distribution of terrestrial ecosystems. Organisms are expected to migrate north or south to cooler latitudes and also to higher altitudes.
- There will be competition between migrating organisms and species in existing communities
- Effect on corals
9
Q
Climate Change
A
- The rise in sea levels associated with global warming will bring many problems for coastal ecosystems which are some of the most productive on Earth.
- Some ecosystems will become even more restricted in their range than is currently the case and some will become even more fragmented
- The frequency of natural catastrophes, such as hurricanes, typhoons, severe storms and flooding is thought to be on the increase.
- Following typhoons in the Pacific, flooding increases the concentration of nutrients in coastal waters.
- This encourages growth of phytoplankton which provides food for the larvae of the crown-of-thorns starfish
10
Q
Why does Biodiversity matter?
A
1) Ethical Reasons
2) To Maintain Ecosystems
3) Damage to food webs
4) Medicinal value of many organisms
5) Income
6) Lost alleles that could be used in genetic engineering
7) Preservation of genetic diversity
8) Practical uses (e.g. dolphins for autistic children)
9) Aesthetic value
10) Their attractive or unusual appearances and different methods of survival
11
Q
Ethical reasons (why biodiversity matters)
A
- We share our planet with a huge range of other organisms and we have no right to drive them to extinction
- Some people believe that humans have custody of the Earth and should therefore value and protect the organisms that share the planet with us
12
Q
Maintaining Ecosystems (e.g. nutrient cycling) (why biodiversity matters)
A
- Forests and peat bogs absorb carbon dioxide and may help to reduce the effect of increases in carbon dioxide in the atmosphere
- Organic waste material added to waters is broken down by microorganisms.
- The transpiration of plants contributes to the water cycle providing us with drinking and irrigation water.
- Termites and ants along with many species of fungi and bacteria recycle elements, such as carbon, nitrogen, sulfur and phosphorus.
- Without this recycling, the supply of nitrates, sulfates and phosphates for plants would become limiting.
- Plant growth would slow and there would be less food available for organisms in other trophic levels
13
Q
Damaging food webs (why biodiversity matters)
A
- In general, the higher the diversity of an ecosystem, the less likely it is to be unbalanced by changes in conditions or threats such as pollution
- All the organisms in an ecosystem interact in many different ways, and, as we have seen,
- If one key species disappears, this can affect the whole community. We are part of many ecosystems and rely on them in many ways
14
Q
Medicinal value of many organisms (why biodiversity matters)
A
- Ecosystems are of direct value to humans. Many of the drugs that we use originate from living organisms. Antibiotics are isolated from fungi and bacteria
- There is currently much interest in cataloguing plants used in traditional Chinese and Indian medicines to see if they can provide drugs that can be mass-produced.
- There are doubtless many more that we do not know about. If we allow tropical forests with their great biodiversity to disappear, then we are undoubtedly losing species that could be beneficial to us
15
Q
Income (why biodiversity matters)
A
- Wildlife is a source of income for many countries as ecotourism has increased in popularity.
- Countries such as Belize, Malaysia, the Maldives and Costa Rica encourage tourists to visit their National Parks.
- This form of tourism provides employment and contributes to the economies of these nations.
