More than 30 years ago, I worked on what may have been the first Nature-Based Solutions (NBS) project. This was an agroforestry project in Guatemala that the energy company AES funded as the first corporate carbon offset project. AES wanted to offset the emissions of a small coal-fired power plant it was building in Thames, Connecticut. The agroforestry project had as its goal increasing sustainability of local land use and conserving surrounding tropical forest (and thus conserving carbon).
Later, I authored some of the earliest studies of NBS potentials while at the World Resources Institute, and I continued that work with the Intergovernmental Panel on Climate Change. I’ve continued to track what is now a substantial NBS literature; you can explore this literature in our open access Nature-Based Solutions Roadmap in the Climate Web, a climate change knowledge management solution.
Nature-Based Climate Solutions
Nature-based solutions references a category of mitigation solutions, otherwise referred to as natural climate solutions, based on preserving, restoring, or expanding biological stores of carbon on land or in the oceans. Whether we’re talking about protecting tropical rainforests, rewilding temperate zones, restoring soil carbon levels on agricultural lands, or sinking seaweed into the deep ocean, we’re talking about NBS.
Hundreds of studies have now explored how large-scale NBS options might contribute to climate change mitigation and the achievement of global climate targets. More recently, there has been an increasing focus on the use of NBS options in adapting to climate change, whether in the form of urban forestry (local cooling) or mangrove forests (as a sea level rise and storm surge buffer), and other ideas.
Today nature-based solutions are widely characterized as being key to the achievement of either the 1.5 or 2 degree C global temperature targets. A July 2019 Guardian headline sticks in my mind as a telling example of how people are enthusiastically characterizing NBS potentials: Tree planting ‘has mind-blowing potential’ to tackle climate crisis. Similar headlines have characterized the mitigation potential of NBS options from agricultural soils to holistic grazing.
As a result NBS options have become core to corporate “Net Zero by 2050” commitments, as well as plans to radically expand voluntary carbon markets. It’s probably safe to say that neither of these initiatives would be happening without the expectation of being able to rely on large-scale and low-cost nature-based solutions.
I’ll admit that I’m skeptical of the practicality of many of the expansive claims being made regarding NBS potentials today. We’ve been trying to conserve tropical forests and promote more sustainable agricultural practices for several decades now, for example, without much systemic change to show for the effort. Why should we assume now that the barriers that have impeded NBS progress up to this point can suddenly be overcome?
But for purposes of this short review, I’ll set aside the question of how much carbon could plausibly be conserved or stored in today’s forests, soils, and oceans. Instead, I’ll raise the increasingly uncertain question of how much of that conserved carbon will still be mitigating climate change in 2050 or 2100.
What If 3.5 Degrees C is the Best We Can Do?
Very recently risk expert George Backus released a new analysis suggesting, based on simulation modeling, that 3.5 degrees C is likely to be the best the world will be able to do when it comes to average global temperature rise by 2100. To be clear -- the study doesn’t forecast 3.5 degrees C as the most likely outcome; rather, it suggests it is the best case outcome. You can find an assessment of the study’s methodology and conclusions here, noting that even that depressing number comes with some optimistic assumptions.
Can natural systems — and by association many nature-based solutions — continue to mitigate climate change in the face of an average global temperature rise even remotely close to 3.5 degrees C? There is a substantial literature on the ability of natural systems to adapt to climate change, but much less attention has focused specifically on the ability of nature-based solutions to do so.
What we do know is that a lot of natural systems are extremely sensitive to changing temperatures, not to mention precipitation extremes, droughts, sea level rise, and more. The figure below from 2010 forecasts the increase in annual area likely to be burned across the Western U.S. per 1 degree C of average temperature change. You can see in the figure that the impact ranges widely, reaching 750% in one case. Per 1 degree! Those are sensitive ecosystems.
The ability of NBS to adapt to a changing climate will vary by solution type, geography, and the climate scenario being used. But there aren’t a lot of graphics that do as nice a job of illustrating the issue as this one from Jan-Francois Bastin’s 2019 look at “The Global Tree Restoration Potential.” The study does suggest a large mitigation potential for trees, but this graphic shows how much tree cover might be lost by 2050 due to climate change itself.
Needless to say, the outcome suggested in the image above would leave A LOT of corporate Net Zero Commitments and voluntary offsets in trouble, if not entirely in ruins. What liabilities or brand-related risks might be created as a result?
Rethinking Our NCS Assumptions?
As we rush to expand implementation of nature-based solutions, there are several things that worry me about business and societal reliance on them in seeking to mitigate climate change.
Climate change seems to be accelerating, which means we’ll probably see more fires, droughts, and floods, among other impacts. All of these will challenge nature-based solutions.
Nature-based solutions are much more sensitive to changes in the extremes around a gradually rising average global temperature than to the average itself. My suspicion is that relatively few studies of natural system adaptation to climate change have adequately incorporated the impact of climate variability on extremes in a warming world and the implications for NBS.
George Backus’ recent study suggesting that we will have to deal with a minimum of 3.5 degrees C of average global temperature change by 2100 would seem to jeopardize the whole idea of NBS. While nature-based solutions of all kinds would likely face significant challenges under a 1.5 2.0 degrees C scenarios given climate changes we’re already seeing, 3.5 degrees seems likely to be well beyond the adaptation limits of most NBS.
One expert recently noted in a personal communication that:
“Natural climate solutions are well intentioned and sound nice but are decades too late and are now a delusional distraction.”
The bottom line? Anyone focused on Net Zero by 2050 commitments, or who is interested in expanding voluntary carbon markets, should be checking (and double-checking!) their assumptions about the ability of nature-based solutions to perform under plausible future scenarios. The implications could be serious indeed. Net Zero by 2050 commitments and voluntary carbon markets could result in fewer emissions reductions in the near term, while the carbon originally stored is released back into the atmosphere as temperatures rise. Failing to seriously consider these issues would represent a horrendous example of willful blindness, comparable to installing a fire suppression system in your business with the label: Warning – May Fail in Extreme Heat.
Note: If this piece calling for a review of our assumptions regarding nature-based solutions is relevant to your decision-making, visit our Climate Assumptions Audit website for more information about the business importance of challenging climate change assumptions, and how to do so.
We've discussed this a lot in-house, and the main conclusion is that if we go that far it's game over anyway. Bronson Griscom made that point in Episode 54 of Bionic Planet (Give us Ecotopia or Give us Death).
That's one reason I abandoned my hard line on the issue of additionally in Improved Forest Management: all forests are going to need more maintenance in the coming years. We now live on a managed planet.
This goes to the points you and Allie Goldstein made in Asheville (and which I featured in Episode 66): we can't adapt our way out of this.
To me, this is an argument for pulling out the stops to end deforestation and ramp up management of forests now -- while also driving down industrial emissions.
I actually see these net zero commitments as something of a distraction if they only focus on 2050 targets. We need to be emphasizing net zero eventually but carbon neutral now.