3.2 Human impact on biodiversityIB Environmental Systems and Societies HL: Revision notes

Biodiversity is adversely affected by direct influences (harm by the activity itself: hunting, overfishing, habitat clearance, introducing species) and indirect influences (changes to the environment such as pollution, nutrient runoff and climate change, or loss of a species affecting others). Most ecosystems are subject to multiple human impacts that combine.

Invasive alien species can reduce local biodiversity by competing for limited resources, predation, and introducing diseases or parasites.

Example: the brown tree snake on Guam preyed on native birds that had no defences; 10 of the 12 native forest bird species disappeared from most of the island. The Guam kingfisher survives only in captivity.

The IUCN assesses global conservation status and publishes the Red List: Least Concern, Near Threatened, Vulnerable, Endangered, Critically Endangered (threatened), Extinct in the Wild, Extinct; also Data Deficient and Not Evaluated. A status publicises vulnerability and lets governments, NGOs and citizens select conservation priorities.

Three named species are required: one extinct through human activity (e.g. thylacine, passenger pigeon), one critically endangered (e.g. Sumatran orangutan) and one whose status was improved by intervention (e.g. Arabian oryx, giant panda).

The tragedy of the commons describes the outcome of shared, unrestricted use of a resource: each user gains from taking more while the cost of depletion is shared, so the resource is over-used. Examples: open-access fisheries, grazing land and the atmosphere. Solutions include quotas, licences, community management and international agreements.

(HL) Biodiversity hotspots are regions with at least 1,500 endemic vascular plant species that have lost at least 70% of their original habitat. Habitat destruction there could lead to a significant loss of biodiversity, especially in tropical biomes, because many species are endemic and specialised. Example: the Atlantic Forest, Brazil, with only about 12–16% of its forest remaining.

(HL) Key biodiversity areas (KBAs) are areas identified as priorities for conservation on the basis of the international importance of their species and habitats.

(HL) Conflict in KBAs: there is conflict between exploitation (mining, logging, farming), sustainable development and conservation. Example: Virunga National Park in the Democratic Republic of the Congo, home to mountain gorillas, has faced oil exploration, charcoal production and armed conflict.

(HL) Traditional indigenous approaches to land management can be seen as more sustainable (built up over generations, with cultural and spiritual values and stewardship), but they face challenges from population growth, economic development, climate change and a lack of governmental support and protection. Example: indigenous territories in the Brazilian Amazon have lower deforestation than surrounding land but face illegal mining and logging.

(HL) Environmental justice must be considered in conservation: fair treatment and participation of all people, avoiding displacement of communities, and sharing the benefits of conservation.

(HL) The planetary boundary loss of biosphere integrity indicates that species extinctions have already crossed a critical threshold: current extinction rates are far above the natural background rate.