Healthy ecosystems crucial for reaching climate targets

Earth’s ecosystems have played a central role in keeping our planet’s climate system unusually stable throughout the last 11,700 years.  Today, ocean and land ecosystems remove around 50% of human induced CO2 emissions from the atmosphere each year. Without this biosphere carbon storage, current international climate targets cannot be met. Therefore, alongside efforts to transition away from fossil fuels, deforestation, environmental degradation and loss of biodiversity must be halted immediately, researchers argue in a recent opinion paper in PNAS, and biosphere stewardship is key.

Taken for granted in climate models

All major global climate models whose simulations give us hope of meeting the target of the Paris Climate Agreement—to keep warming well below2 °C—take the continued provision of this gigantic biosphere endowment for granted. This means that the ability of intact nature to continue to sequester carbon is already in the estimate of the remaining carbon budget to hold to the Paris climate target. However, this fundamental assumption relies on terrestrial and marine ecosystems remaining intact and resilient to human pressures, even as climate change progress. Instead, more than 75% of the land surface has been altered by humans, removing 50% of vegetation biomass, and less than 5% of the oceans remain free from human interference. Today, major carbon sinks exist in remaining intact tropical, temperate, and boreal forests.

The research team, led by Beijer Fellow Johan Rockström, Director of the Potsdam Institute for Climate Impact Research, and including Beijer Institute director Carl Folke, warn that the systems may be reaching tipping points:

“Human activities driving deforestation and degradation have already turned the Brazilian Amazon into a carbon source , and other tropical biomes may be moving toward a similar fate”, they write and add:  “Global warming also increases risks of wildfires in temperate and boreal forests, which could flip Northern hemisphere ecosystems from sink to source in coming decades.”

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Biosphere stewardship necessary to to keep under 3 degrees

Without this natural carbon storage, the team calculates that by 2100, global mean temperature would be moving decisively toward 3 °C warming, even with the rapid decarbonisation actions assumed in the most positive climate scenario used by IPCC, and also the only one that meet the goals of the Paris agreement. They call for biosphere stewardship, which implies a fundamental shift in governance from only reducing human pressures, to managing nature actively to promote human wellbeing, also for future generations. This include that critical biomes should be recognized as global commons in service of humanity.

Three urgent global transformations

They list three urgent global transformations to avoid a climate catastrophe:

A transformation of the energy system that cuts emissions by half each decade to reach netzero by 2050; a transformation of the agriculture and forestry sectors from greenhouse gas sources to sinks within 30 years; and a transformation of our relationship with nature to one that conserves, restores, and enhances its benefits for people and planet. Each must begin immediately.

“Biosphere stewardship is an indispensable guiding principle and building block for the successful implementation of these transformations,” they write.

The team go on to listing three strategic considerations, including translating the overall framing of biosphere stewardship into actionable paths for all sector and actors in society. They see that the massive spending by governments in response to the Covid-19 pandemic can be a once-in-a-generation opportunity to achive transformation, if this immense stimulus is aligned with biosphere stewardship principles.