ENVIRONMENT: The Anthropocene Carbon Budget and Ecosystem Tipping Points Global carbon sinks—forests, wetlands, and oceans—have absorbed roughly 55% of human CO₂ emissions since 1750, but their absorption capacity is declining as they approach saturation. The Amazon rainforest, which historically sequestered 2 gigatons of CO₂ annually, has shifted toward net carbon release in some regions due to deforestation exceeding 17% of original forest cover. Meanwhile, ocean acidification has increased 30% since pre-industrial times, fundamentally altering marine calcification rates and disrupting food webs that support 3+ billion people. Understanding these feedback mechanisms matters because we're operating within a rapidly shrinking "remaining budget"—roughly 250 gigatons of CO₂ before 1.5°C warming becomes mathematically unavoidable—making the difference between managed transition and cascading ecosystem collapse a matter of years, not decades.