A4.2.3 Causes of anthropogenic species extinction Notes

Causes of Anthropogenic Species Extinction: Exploring the Sixth Mass Extinction

1. The current rate of species extinction is estimated to be 100 to 1,000 times the natural background rate.
2. This is fueled by interconnected anthropogenic factors like overexploitation, habitat destruction, and climate change.

The Primary Drivers of Anthropogenic Extinction

1. Overexploitation: Unsustainable hunting, fishing, and harvesting of species.
2. Habitat destruction: The conversion of natural habitats into agricultural land, urban areas, and industrial zones.
3. Invasive species: Non-native species introduced by humans that outcompete or prey on native species.
4. Pollution: The contamination of ecosystems with harmful chemicals, plastics, and waste.
5. Climate change: Rapid shifts in environmental conditions caused by human-induced global warming.

Case Study 1: North Island Giant Moa (Dinornis novaezealandiae)

1. The North Island giant moa was a flightless bird endemic to New Zealand, standing up to 3.6 meters tall and weighing 230 kilograms.
2. It played a vital ecological role in seed dispersal and vegetation control.

What Happened?

1. Human Settlement:
   1. Polynesians arrived in New Zealand around the 13th century.
   2. With no natural predators, moa populations were highly vulnerable to hunting.
2. Overhunting: Moa were hunted to extinction in less than 200 years.

Impact on Ecosystems

1. The loss of moa disrupted forest regeneration, as seeds previously dispersed by these birds could no longer travel far from parent plants.

Case Study 2: Caribbean Monk Seal (Neomonachus tropicalis)

1. The Caribbean monk seal was the only pinniped native to the Caribbean Sea.
2. It provided key ecosystem services by maintaining balance in marine food webs.

What Happened?

1. Overhunting: European colonists hunted the seals for blubber, which was rendered into oil.
2. Habitat Destruction: Coastal tourism and urbanization degraded the seals’ breeding habitats.
3. Extinction: The species was declared extinct in 2008 after decades of unsuccessful conservation attempts.

Ecosystem Consequences

1. The loss of the monk seal altered predator-prey dynamics,
2. This potentially contributed to overpopulation of certain fish species and disrupting coral reef health.