Threats to biodiversity

Biodiversity is under threat in many aquatic and terrestrial ecosystems as human population continues to increase and we take more resources from the environment and produce more waste.








Threats to biodiversity:

• habitat loss and degradation of the environment
• climate change
• excessive use of fertilisers --> pollution
• overexploitation and unsustainable use of resources
• alien species invasion on native species

1. Habitat loss 

- destruction of natural environment: land clearing for agriculture, housing, transport,...

- e.g.: deforestation --> soil erosion --> sever land degradation

=> habitat fragmentation (habitats become divided)

• most at risk of extinction: endemic species on small islands

2. Climate change

Air pollution: combustion of fuel with high sulfur content leads to high concentrations of atmospheric SO₂

    SO₂  in atmosphere + H₂O = acid rain

• destroys vegetation
• acidification of aquatic ecosystems: animals can't breed/survive in waters of low pH

Industrialisation, extraction and combustion of fossil fuels

    increases concentration of CO₂ and CH₄ in the atmosphere = greenhouse gas --> climate change

    ---> global warming

• change in distribution of terrestrial ecosystems: organisms will migrate north or south to cooler and higher latitudes. There will also be competition between migrating organisms
• acidification of the oceans: destroy CaCO3 mollusc shells
• rise in sea levels
• increase in the frequency of natural catastrophies (hurrican, flooding,...)

                     e.g.: flooding: increases the concentration of nutrients in coastal waters -->                                        increases growth of phytoplanktons which provides food for starfish larvae -->                              adult starfish eats the coral

• coral bleaching: corals provide protection for many coastlines. Corals are very sensitive to temperature increases --> die

3. Fertilisers and pollution

*pollutant: substances that animal bodies are unable to metabolise or excrete

• factory wastes flow into rivers without any treatment --> substance persists --> enters food chains --> weakening of immune systems and reduction in fertility in birds and mammals
• marine pollutant: non-biodegrable plastic

                 e.g.: - animals (dolphins) get caught in discarded fishing nets and die

                         - turtles eat plastic bags, mistaken then for jellyfish --> chokes

• excess fertilisers (not absorbed by crop plants) drain into river --> extra nutrients cause growth of producers, such as algae:

                         -  produce toxic substances

                         - algae growth unbalances food web

18.3 Conservation Maintaining biodiversity is important for many reasons. Actions to maintain biodiversity must be taken at local, national and global levels.   It is important to conserve ecosystems as well as individual species. a) discuss the threats to the biodiversity of aquatic and terrestrial ecosystems (see 18.1b)  b) discuss the reasons for the need to maintain biodiversity  c) discuss methods of protecting endangered species, including the roles of zoos, botanic gardens, conserved areas (national parks and marine parks), ‘frozen zoos’ and seed banks  d) discuss methods of assisted reproduction, including IVF, embryo transfer and surrogacy, used in the conservation of endangered mammals  e) discuss the use of culling and contraceptive methods to prevent overpopulation of protected and non-protected species  f) use examples to explain the reasons for controlling alien species  g) discuss the roles of non-governmental organisations, such as the World Wide Fund for Nature (WWF) and the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), in local and global conservation  h) outline how degraded habitats may be restored with reference to local or regional examples