Decline of Biodiversity

3. Extinction debt

-Study of 10,000 wildlife populations suggests that earth has lost 50% of individual animals since 1970. -Doesn't mean that they have gone extinct, but may be on path to extinction.

Past extinctions were caused by

-climate change -plate tectonics -asteroid impacts

Reasons for estimated extinction rates being lower than expected

1. Effective short-term conservation efforts (habitat conservation, management, captive breeding, translocation) 2. Species surviving better in human-modified environments (2nd growth) than expected. 3. "Extinction debt": extinction is often a slow process; species hang on for a while even after habitat is degraded, but eventually may be doomed to extinction because they fail to reproduce at a replacement rate --> loss of genetic diversity. 4. Species are going extinct before we are able to document them.

Proximate causes of biodiversity loss

1. Habitat destruction & degradation 2. Climate change 3. Pollution 4. Hunting / direct mortality 5. Invasive species

Questions reagarding the loss of biodiversity in modern times

1. How many & what species are currently being lost (or at greatest risk)? 2. What are the specific causes of this crisis? 3. What is being done to help solve the issue?

Groups taking actions to slow decline

1. Individual 2. Corporations 3. Non-profit 4. Science 5. Government

Underlying / ultimate causes of biodiversity loss

1. Social change & development; demand for resources 2. Population growth; >3% in many economically developing countries 3. Commercial markets; whale meat, hardwoods, traditional medicines 4. Public policies that create inequality & poverty; force people to hunt for food or kill animals for income; ivory 5. Macro-economic policies; globalizing role of transnational corporations

Currently might be:

6th mass extinction -40,000 -27,000-100,000; 20% of all species gone by 2020 -250,000; all species gone by 2010-2025 We haven't seen mass extinctions of this magnitude yet.

Current major threats / causes of biodiversity loss

HIPPO -Habitat destruction & degradation -Invasive species (& emerging infectious disease) -Pollution -Population growth -Over exploitation -Climate change

2. Nature more resilient than believed

Hula Painted Frog -Believed extinct in 1955 after the draining of Lake Hula & the associated marshes in N. Israel -Re-discovered in 2011 after restoration of these marshes over the past 20 years; >100 individuals found in 2016. -How long can it survive?

4. Haven't even identified many species

Some may have gone extinct or will go extinct before we know they exist.

1. Effective short-term conservation efforts

Some solutions are working in the short-term at least. -whooping crane

Endangered (or imperiled) species

a species or subspecies that is at risk of extinction throughout all or part of its range

>90% of

forest along Atlantic coast of Brazil cleared over past 100 years -no known extinctions

Number 1 cause of biodiversity loss

habitat destruction & degradation

Threatened (or vulnerable) species

possibly at risk of extinction in the near future

99% of

primary forest of eastern US lost from 1800-1960s -only 1 or 2 bird species went extinct

Extirpation

the loss of a species at a local scale

Extinction

the loss of a species at the global scale

Only ______ confirmed extinctions since 1500 AD

~800 -most due to over hunting