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.

Case Study 3: Passenger Pigeon (Ectopistes migratorius)

1. Once numbering in the billions, passenger pigeons were among the most abundant birds in North America.
2. Their massive flocks played critical roles in seed dispersal and forest dynamics.

What Happened?

1. Mass Hunting: 19th-century hunters used advanced firearms and transportation networks to decimate pigeon populations.
2. Deforestation: Widespread logging destroyed nesting and feeding habitats.
3. Extinction: The last known passenger pigeon, Martha, died in captivity in 1914.

Common Themes in Anthropogenic Extinction

Across these case studies, several consistent patterns emerge:

1. Overexploitation: Hunting or harvesting species faster than their populations can recover.
2. Habitat Destruction: Permanent loss of critical breeding and feeding areas.
3. Lack of Awareness: Early human settlers and industrial societies often underestimated the long-term consequences of their actions.
4. Ecological Impact: The extinction of key species disrupts food webs and reduces ecosystem resilience.

Why Does This Matter?

Biodiversity loss affects not just the environment but also human well-being:

1. Ecosystem Services: Pollination, clean water, and climate regulation depend on healthy ecosystems.
2. Economic Impacts: Fisheries, agriculture, and tourism suffer when ecosystems collapse.
3. Ethical Responsibility: Protecting species is a moral imperative for current and future generations.

What Can Be Done?

To combat the sixth mass extinction, conservation efforts must address the root causes of biodiversity loss. Strategies include:

1. Legislation and Policy: Enforcing laws against overexploitation and habitat destruction.
2. Protected Areas: Establishing reserves to safeguard critical habitats and species.
3. Restoration Ecology: Rewilding degraded ecosystems to restore ecological balance.
4. Sustainable Practices: Promoting sustainable hunting, fishing, and agricultural methods.
5. Global Cooperation: Tackling transboundary issues like climate change and invasive species through international collaboration.