Climate and biodiversity

Paris climate goals unattainable without rich biodiversity and ecosystems

Pine tree forest near mountain under sunset.

To meet the world’s climate goals we must maintain and even strengthen natural carbon sinks in forests, oceans and other ecosystems. Photo: S. A/Unsplash

Large-scale conservation and restoration of natural carbon sinks in forests, oceans and other ecosystems is an existential must for humanity

Story highlights

  • Ocean and land ecosystems remove around half of human carbon dioxide emissions from the atmosphere each year
  • Due to degradation of nature, humanity can no longer take for granted this capacity of the biosphere to dampen greenhouse gas emissions
  • Governments and businesses must promote biosphere stewardship that strengthens and secures natural carbon sinks to have a chance to achieve the Paris climate targets

HELPING NATURE HELP US: Our forests, grasslands, kelp forests and other ecosystems still manage to remove around half of all the carbon dioxide we humans emit to the planet’s atmosphere every year.

This means that half of our ‘climate debt’ is removed, for free, by the biosphere every year—a vast subsidy to the world economy.

In an Opinion piece in the journal PNAS, former centre directors Carl Folke and Johan Rockström with colleagues from Germany and the US make clear that safeguarding the biosphere from further degradation is “an existential challenge for humanity.”

Ahead of the UN climate meeting in Glasgow, COP26, their message is clear:

If climate science tells us that we need to reach net-zero emissions by 2050, then ecological science commits us to a to net-zero loss of biodiversity and ecological functions from 2020 onwards.

Without biodiversity and rich ecosystems on land we would have exceeded the 1.5°C Paris climate limit already today, with serious impacts on all societies.

Johan Rockström, lead author

The risk of tipping points

Humans have altered more than 75% of the land surface and more than 95% of the oceans, however, relatively intact ecosystems have been remarkably resilient to climate change.

Actually, the overall carbon sink of forests and other land ecosystems has even increased in response to elevated carbon dioxide levels – in particular in the Northern hemisphere, the authors note. And ecosystems on land store almost four times the current atmospheric CO2 content.

Now, the world seems to be approaching a tipping point with challenging effects for both societies and ecosystems:

  • The Brazilian Amazon has already turned into a carbon source due to deforestation, higher temperatures and increased frequency of droughts and wildfires

  • Temperate and boreal forests are also impacted in ways that could shift Northern hemisphere ecosystems from sinks to sources in coming decades.

“Not only have human pressures on Earth reached dangerously high levels, but we see signs that humanity may no longer be able to count on the capacity of the biosphere to continue dampening greenhouse gas emissions and hold onto its carbon stocks,” the authors write.

Three action areas

Hence, to meet the world’s climate goals we must maintain and even strengthen natural carbon sinks in forests, oceans and other ecosystems. For this to happen, the authors list three main action areas:

  1. Governments should promote Natural Climate Solutions (NCS) by applying land management practices that conserve, restore, or sustainably manage natural ecosystems and working lands.

    NCS could deliver a third of global emission reductions needed by 2030, and could limit warming by an additional 0.3 °C by the end of the century (difference between blue and green line in figure).

  2. Biosphere stewardship must be translated into actionable paths for all sectors and actors in society.

    For example, governments should include NCS in their national plans for contributing to the Paris agreement; cities and businesses should set science-based targets for natural carbon sinks; and local communities, faith-based organizations, and civil society groups all have vital roles to play.

  3. New financial mechanisms and policies must be implemented.

    Governments and businesses should e.g. adopt full costing of environmental externalities, natural capital accounting, sustainability principles to guide financial investments, remove all direct subsidies to the fossil fuel industry, and adopt a sufficiently high global tax on carbon.

IPCC has recently concluded that Earth’s temperature is more sensitive to rising carbon dioxide concentrations than previously thought.

If we add the risk of forest tipping points and abrupt permafrost thaw, the estimated remaining carbon budget to achieve the Paris targets could disappear altogether.

(A) Major carbon sinks in biomes around the world (grey areas are dominated by agriculture). (B) Carbon stocks in major biomes and how much of each biome that remains pristine today. (C) Global average temperature changes under the RCP2.6 IPCC scenario (“Paris target” is the standard simulation and “Biosphere loss” shows change without land carbon sinks from 1900). The Δ0.4 °C arrow shows the estimated dampening effect today from land-based ecosystems. “Full NCS” (Natural Climate Solutions) assumes large-scale conservation and restoration of forests, grasslands, peatlands, and wetlands.

Methodology

To assess the future influence of biosphere stewardship on the climate, the researchers used a model called MAGICC6. More specifically, they examined what would happen (now and in the future) if ecosystems on land had stopped absorbing carbon dioxide from 1900 and onwards. The resulting changes in global mean temperature were calculated under the so-called RCP2.6 emission scenario, the only of the IPCC scenarios that aligns with the Paris agreement (blue line in figure).

This revealed that without resilient carbon sinks in the biosphere it will be impossible to hold global warming well below 2 °C (red line in figure). We are also more and more likely to experience major changes in ecosystems if global warming exceeds 1.5 °C, triggering increased release of greenhouse gases and other feedbacks that risk accelerate warming further. Hence, active stewardship that build resilience of the climate regulation service of the biosphere is a precondition for a prosperous future.

Link to publication

Topics: Biodiversity
Published: 2021-10-17