Avoiding catastrophic climate change requires rapid decarbonization and improved ecosystem stewardship. To achieve the latter, ecosystems should be prioritized by responsiveness to direct, localized action and the magnitude and recoverability of their carbon stores. Here we show that a range of ecosystems contain 'irrecoverable carbon' that is vulnerable to release upon land use conversion and, once lost, is not recoverable on timescales relevant to avoiding dangerous climate impacts. Globally, ecosystems highly affected by human land-use decisions contain at least 260 gigatonnes of irrecoverable carbon, with particularly high densities in peatlands, mangroves, old-growth forests and marshes. To achieve climate goals, we must safeguard these irrecoverable carbon pools through an expanded set of policy and finance strategies. Main TextScientific assessments provide increasingly strong evidence that global warming in excess of 1.5 ˚C above pre-industrial levels may trigger irreversible changes to the Earth system, with far-reaching social and economic costs for human societies around the world 1 . Limiting warming to 1.5 ˚C, according to the Intergovernmental Panel on Climate Change (IPCC), requires the world to slow global emissions immediately and reach net zero carbon dioxide (CO 2 ) emissions by around 2050.To do this, the IPCC estimates that our remaining carbon budget as of 2017, or the amount of CO 2 we can add to the atmosphere between now and mid-century, is about 420 gigatonnes (Gt), equal to about 114 Gt of carbon, for a two-thirds chance of staying below 1.5 ˚C1 . Given emissions have not slowed since 2017, as of 2020, this carbon budget will be spent in approximately eight years at current emissions rates 2 . Staying within this carbon budget will require a rapid phase-out of fossil fuels in all sectors as well as maintaining and enhancing carbon stocks in natural ecosystems, all pursued urgently and in parallel 3-6 . Natural climate solutions, which promote conservation, restoration, and improved land management to increase carbon sequestration or reduce emissions from ecosystems and agricultural lands, could provide a quarter or more of the cost-effective mitigation (i.e. ≤USD100 / t CO 2 e) needed by 2030 [7][8][9] .These natural climate solutions focus on either turning down the 'dial' of emissions, for example by preventing the conversion of ecosystems to other land-uses, or turning up the dial on ecosystems' ability to remove CO 2 from the atmosphere via restoration or enhanced productivity. Yet uncertainty remains regarding the responsiveness of various ecosystem carbon stocks to management actions and regarding the relative reversibility of their loss. Are there ecosystem carbon stocks that, if lost, could not recover within a time scale meaningful to the remaining carbon budget? Any loss of such 'irrecoverable' carbon stocks would represent an effectively permanent debit from our remaining carbon budget. Ecosystems containing irrecoverable carbon may thus warrant distinct and unwavering conser...

Protected areas are intended to safeguard biodiversity in perpetuity, yet evidence suggests that widespread legal changes undermine protected area durability and efficacy. We documented these legal changes—protected area downgrading, downsizing, and degazettement (PADDD) events—in the United States and Amazonian countries and compiled available data globally. Governments of the United States and Amazonian countries enacted 269 and 440 PADDD events, respectively. Between 1892 and 2018, 73 countries enacted 3749 PADDD events, removing 519,857 square kilometers from protection and tempering regulations in an additional 1,659,972 square kilometers; 78% of events were enacted since 2000. Most PADDD events (62%) are associated with industrial-scale resource extraction and development, suggesting that PADDD may compromise biodiversity conservation objectives. Strategic policy responses are needed to address PADDD and sustain effective protected areas.

Avoiding catastrophic climate change requires rapid decarbonization and improved ecosystem stewardship at a planetary scale. The carbon released through the burning of fossil fuels would take millennia to regenerate on Earth. Though the timeframe of carbon recovery for ecosystems such as peatlands, mangroves and old-growth forests is shorter (centuries), this timeframe still exceeds the time we have remaining to avoid the worst impacts of global warming. There are some natural places that we cannot afford to lose due to their irreplaceable carbon reserves. Here we map ‘irrecoverable carbon’ globally to identify ecosystem carbon that remains within human purview to manage and, if lost, could not be recovered by mid-century, by when we need to reach net-zero emissions to avoid the worst climate impacts. Since 2010, agriculture, logging and wildfire have caused emissions of at least 4.0 Gt of irrecoverable carbon. The world’s remaining 139.1 ± 443.6 Gt of irrecoverable carbon faces risks from land-use conversion and climate change. These risks can be reduced through proactive protection and adaptive management. Currently, 23.0% of irrecoverable carbon is within protected areas and 33.6% is managed by Indigenous peoples and local communities. Half of Earth’s irrecoverable carbon is concentrated on just 3.3% of its land, highlighting opportunities for targeted efforts to increase global climate security.

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Near real-time (NRT) forest monitoring and alert systems based on remotely sensed data are among the most recently developed tools to help manage and protect forest resources. The use of satellite and airborne remote sensing to quickly and accurately detect activities associated with deforestation has great potential for catalyzing local response teams responsible for assessing and interdicting threats to tropical forest ecosystems. To better understand the utility of NRT monitoring technologies in improving environmental protection and management, from 2008 to 2016 Conservation International conducted a series of surveys and interviews with users of these systems in four countries where wildfires threaten tropical forest ecosystems: Madagascar, Indonesia, Bolivia and Peru. Users reported that NRT forest monitoring systems made significant contributions to improving the ability of conservation and forest management organizations to respond to and reduce the impacts of fire, deforestation and other illegal or undesirable forest activity. Understanding the types of applications for which users successfully employed forest monitoring data, the challenges they faced in accessing, analyzing or disseminating these data, and the lessons learned from our attempts to develop and deploy NRT forest monitoring systems is useful to institutions interested in successfully incorporating NRT monitoring into their work.