How do humans affect biodiversity?

Humanity impacts the planet's biodiversity in multiple ways, both deliberate and accidental. The biggest threat to biodiversity to date has been the way humans have reshaped natural habitats to make way for farmland, or to obtain natural resources, but as climate change worsens it will have a growing impact on ecosystems.

The main direct cause of biodiversity loss is land use change (primarily for large-scale food production) which drives an estimated 30% of biodiversity decline globally. Second is overexploitation (overfishing, overhunting and overharvesting) for things like food, medicines and timber which drives around 20%. Climate change is the third most significant direct driver of biodiversity loss, which together with pollution accounts for 14%. Invasive alien species account for 11%. 

Some models predict that climate change will become the primary cause of biodiversity decline in the coming decades. The impact of all the main drivers of biodiversity loss is accelerating and, as a consequence, so is the pace of biodiversity decline.

Growing demand for natural resources due to the increasing human population, more rapidly increasing per capita consumption and changing consumption patterns has meant that ever more natural habitat is being used for agriculture, mining, industrial infrastructure and urban areas.

Key areas of human activity causing biodiversity loss include:

• Deforestation. Tropical rainforests are particularly rich in biodiversity and are being destroyed
• Habitat loss through pervasive, incremental encroachment such as that caused by urban sprawl
• Pollution such as that associated with widespread pesticide use and overuse of fertiliser which are 6 and 12 times greater than they were before 1961 respectively
• It is estimated that half of the species at risk are threatened by agriculture
• Water use in some of the largest water catchments in the world where dams and irrigation reduce water flows
• Hunting and the over-exploitation of species such as in wild capture fisheries but also for wildlife trade
• Spread of invasive species and diseases through trade and travel 
• Climate change, as warming and changing rainfall patterns alters species ranges and the underlying water and chemical cycles which define current ecosystems 
• Pollution from plastic waste although its long-term effects on biodiversity are far from clear

For more on this issue visit: Amazonia’s future: Eden or degraded landscapes? | Royal Society; Preserving global biodiversity requires rapid agricultural improvements | Royal Society; and Past and future decline and extinction of species | Royal Society