by DOREEN STABINSKY & KATE DOOLEY
Net-zero emissions pledges to protect the climate are coming fast and furious from companies, cities and countries. But declaring a net-zero target doesn’t mean they plan to stop their greenhouse gas emissions entirely – far from it. Most of these pledges rely heavily on planting trees or protecting forests or farmland to absorb some of their emissions.
That raises two questions: Can nature handle the expectations? And, more importantly, should it even be expected to?
We have been involved in international climate negotiations and land and forest climate research for years. Research and pledges from companies so far suggest that the answer to these questions is no.
What is net-zero?
Net-zero is the point at which all the carbon dioxide still emitted by human activities, such as running fossil fuel power plants or driving gas-powered vehicles, is balanced by the removal of carbon dioxide from the atmosphere. Since the world does not yet have technologies capable of removing carbon dioxide from air at any climate-relevant scale, that means relying on nature for carbon dioxide removal.
According to the Intergovernmental Panel on Climate Change, global carbon dioxide emissions will need to reach net-zero by at least midcentury for the world to have even a small chance of limiting warming to 1.5 degrees Celsius (2.7 F), an aim of the Paris climate agreement to avoid the worst impacts of climate change.
The devil of net-zero, of course, lies in its apparent simplicity.
Nature’s potential and its limits
Climate change is driven largely by cumulative emissions – carbon dioxide that accumulates in the atmosphere and stays there for hundreds to thousands of years, trapping heat near Earth’s surface.
Nature has received a great deal of attention for its ability to remove carbon dioxide from the atmosphere and store it in the biosphere, such as in soils, grasslands, trees and mangroves, via photosynthesis. It is also a source of carbon dioxide emissions through deforestation, land and ecosystem degradation and agricultural practices. However, the right kinds of changes to land management practices can reduce emissions and improve carbon storage.
Net-zero proposals count on finding ways for these systems to take up more carbon than they already absorb.
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