IB Environmental systems and societies 3.2A Human Impacts on Biodiversity Notes

Humans Drive Biodiversity Loss Directly and Indirectly

1. Human activity is now the main driver of biodiversity loss, causing species extinctions, habitat degradation, and ecosystem imbalance.
2. Direct threats target organisms themselves, through exploitation and hunting.
3. Indirect threats alter the conditions organisms depend on, such as habitat, climate, and pollution.

Direct Threats: Harvesting, Poaching, and Trade

Overharvesting and Overexploitation

1. Overharvesting means taking a species faster than it can reproduce or recover.
2. It includes overfishing, overhunting, and excessive logging.
3. Once harvesting passes the maximum sustainable yield, populations can collapse and food chains break down.
4. It also strips genetic diversity, leaving survivors more vulnerable to disease and environmental change.

Poaching

1. Poaching is the illegal hunting or capture of wildlife for trade, food, or cultural uses.
2. It targets large mammals and endangered species prized for ivory, skins, horns, or traditional medicine.
3. The bushmeat trade also drives hunting of primates and forest mammals, raising the risk of zoonotic disease.

Illegal Pet and Wildlife Trade

1. The illegal wildlife trade is worth about US$23 billion a year, ranking fourth after arms, drugs, and human trafficking.
2. Traded species include parrots, turtles, primates, snakes, and big cats.
3. It destabilizes wild populations and raises extinction risk.
4. CITES regulates and restricts global wildlife trade to curb it.

Indirect Threats: Changing the Conditions for Survival

Habitat Loss and Fragmentation