1.3 Tipping points in the biosphere

Summary

This chapter assesses scientific evidence for tipping points across the biosphere, which comprises Earth’s ecosystems. Human-driven habitat loss, pollution, exploitation and, increasingly, climate change are degrading ecosystems across the planet, some of which can pass tipping points beyond which a ‘regime shift’ to an alternative (and often less diverse or beneficial) ecosystem state occurs. 

Evidence for tipping points emerges across many biomes. In forests, large parts of the Amazon rainforest could tip to degraded forest or impoverished savanna, while tipping in boreal forests is possible but more uncertain, and whether current temperate forest disturbance could lead to tipping is unclear. In open savannas and drylands, drying could lead to desertification in some areas, while in others encroachment by trees and shrubs could see these biodiverse ecosystems shift to a forested or degraded state. Nutrient pollution and warming can trigger lakes to switch to an algae-dominated low-oxygen state. Coral reefs are already experiencing tipping points, as more frequent warming-driven bleaching events, along with pollution, extreme weather events and diseases, tip them to degraded algae-dominated states. Mangroves and seagrasses are at risk of regional tipping, along with kelp forests, marine food webs and some fisheries, which are known to be able to collapse. 

Together, these tipping points threaten the livelihoods of millions of people, and some thresholds are likely imminent. Stabilising climate is critical for reducing the likelihood of widespread ecosystem tipping points, but tackling other pressures can also help increase ecological resilience, push back tipping and support human wellbeing.