We need biosphere stewardship that protects carbon sinks and builds resilience

Abstract

Earth’s biosphere, its extraordinary and complex web of species and ecosystems on land and in the oceans, drives the life-sustaining cycles of water and other materials that enable all life on Earth to thrive. The biosphere is also a principal driver of immense negative feedback loops in the Earth system that stabilize atmospheric CO2 concentrations and thereby global climate—including carbon sequestration by vegetation, soils, and the oceans. As such, Earth’s ecosystems have played a central role in keeping our planet’s climate system unusually stable throughout the last 11,700 years (i.e., the inter-glacial Holocene). During this epoch, global mean temperatures have oscillated only about 1 °C around the pre-industrial average, providing the unique conditions that allowed human civilizations to flourish. Today, ocean and land ecosystems remove around 50% of anthropogenic CO2 emissions from the atmosphere each year (1), an extraordinary biophysical feat, given that these emissions have risen from approximately 4 gigatonnes of carbon (GtC) per year in 1960 to around 11 GtC per year today. Put another way, half our “climate debt” is removed, for free, by the biosphere every year—a vast subsidy to the world economy. Safeguarding the biosphere from further degradation or collapse is an existential challenge for humanity. There are important steps we can take to contain the damage. Image credit: Shutterstock/Kritskiy-ua. The recent Working Group 1 report of the sixth assessment of the Intergovernmental Panel on Climate Change (IPCC) confirmed this major nature contribution to climate stability, estimating the cumulative carbon sequestration by land and oceans to be 56% of all human-caused emissions between 1850 and 2019 (2). All major global climate models whose simulations give us hope of meeting the target of the Paris Climate Agreement—to keep warming well below 2 °C—take the continued provision of this gigantic biosphere endowment for granted, merely … [↵][1]1To whom correspondence may be addressed. Email: johan.rockstrom{at}pik-potsdam.de. [1]: #xref-corresp-1-1