Threats to Biodiversity

If human actions lead to the destruction of ecosystems, such as wetlands or rainforests, biodiversity on Earth could decrease. This would be bad. Environmental awareness is good!

Threats to Biodiversity As scientists learn more about the effects of human actions on ecosystems, we are paying more attention to decreasing human impact on ecosystems and restoring ecosystems that have been altered.

Overview Threats to biodiversity include: 1. Habitat loss Natural disasters – Volcanic eruptions, wildfires, drought Human activity – deforestation – draining wetlands 2. Alien species Harmless Invasive 3. Overexploitation (Eg: over-hunting)

Extinction Extinction occurs when all the individuals of a species have died How does is occur? – When the death rate of a species exceeds the birth rate – Individuals removed > individuals added

Extinction Even in ecosystems un-affected by humans, things never remain the same forever. Biotic and abiotic features change – Biotic factor: arrival of new leaf-eating insect species – Abiotic factor: decline in rainfall  dry soil These changes might not result in direct extinction, but if the change results in death rate > birth rate for a long time…extinction eventually occurs. 

Patterns of Natural Extinction 1. Background extinction: As ecosystems change over looooong periods of time, some existing species become extinct while new species appear via evolution

Patterns of Natural Extinction 2. Mass extinction: sudden change in ecosystems, making them unsustainable This is believed to have happened 5 times in Earth’s history

Natural Extinction The most famous of these events, the Cretaceous- Tertiary (K-T) extinction 65 million years ago, is thought to have been caused at least in part by a giant asteroid that struck Earth off the coast of Mexico, causing tidal waves and climate-altering dust clouds. Dinosaurs, along with two- thirds of the other species on Earth, were killed off by the K-T extinction.

Causes of Natural Extinction Global cooling due to glaciation – Earth’s elliptical orbit around Sun Increased volcanic activity  global warming Increased CO 2 production  global anoxia Changing sea levels Extra-terrestrial impact

Earth’s 6 th Mass Extinction… …is (theorized) to be happening right now. Uh-oh. Ecologists estimate that the current rate of extinction is X higher than normal background rate In one study, species were assessed. – 39% at risk of extinction

The 6 th Extinction This is being called the “biodiversity crisis” – Def: the current accelerated rate of extinctions

Why does losing another obscure species matter?? Gastric brooding frogs, discovered in Australia in the 1980s, raise their young in their stomachs and secrete a substance that protects them from being digested. This promised to provide a new treatment for human peptic ulcers, which afflict 25 million Americans. But when the species went extinct, scientists abandoned the research.

So What Can We Do? Stewardship: All humans are responsible for taking care of our biosphere – For ourselves – For other human beings – For other organisms – For future generations

Restoration Ecology Def: The renewal of destroyed or degraded ecosystems through human intervention – Goal is to simulate natural processes of regeneration

Don Valley Brick Works: 1891Present day Ecological Restoration converted Toronto’s Don Valley Brick Works into a natural heritage park

Methods: Reforestation – the regrowth of a forest through natural processes or planting Wetlands restoration – water levels are returned to normal Controlling Alien Species – Biocontrol is the use of one species to control the pop. or growth of an undesirable species