Global Climate Action Summit kicks off today in San Francisco with nature-based solutions high on the agenda

Over the past few years the idea that protecting and restoring natural habitats can help us fight climate change has been gaining traction. The Paris Agreement calls on all Parties to acknowledge “the importance of ensuring the integrity of all ecosystems, including oceans, and the protection of biodiversity, recognized by some cultures as Mother Earth”, and around 65% of signatories to the Agreement commit to “green” or “nature-based solutions” in their climate pledges. However, though increasingly prominent in international policy discourse, nature-based solutions have received very little attention in our mainstream media. Until now...

Nature-based solutions in the news
Just ahead of the Global Climate Action Summit which kicks off in San Francisco today, three news stories highlight the enormous value of nature in a warming world. Two appeared this week (one on National Geographic’s website and one on the BBC’s) while a third was published as an Opinion piece in the New York Times only a couple of weeks back.

The BBC article ('Nature-based' green house gas removal to limit UK climate change) highlights the key recommendations of a new joint report by the UK Royal Society and the Royal Academy of Engineering. It emphasises how planting 1.2 million hectares of forest (an area over seven times the area of Greater London) should be an immediate priority if the UK is to achieve zero net emissions of carbon dioxide by 2050. The article in National Geographic (Forests Are the Forgotten ClimateSolution, Experts Say) discusses the ambitious target to meet 30% of the Paris Agreement’s emissions reduction goal by 2030 through the sustainable management of forests, the so-called 
30x30 solution which is the subject of talks in San Fransisco tomorrow. Meanwhile, the New York Times  Opinion piece (How California can help save the Amazon) argues that California should help slow deforestation and restore damaged rainforests through a cap and trade system for reducing greenhouse gas emissions. It claims that “Governor Brown has the opportunity to make his biggest impact yet by harnessing the power of forests to reduce carbon dioxide pollution, the principal cause of global warming” and setting a “California standard for forest credits to unlock a private market”.

Nature-based solutions are more than forests, and not all forests are equal
While I am encouraged by these news stories, I am also worried by aspects of the narrative emerging in the mainstream media. In these articles (and indeed in the Paris Agreement itself) the emphasis is on forests; the focus is on managing, protecting and restoring forests and/or planting new forests. In one sense this is justifiable: the loss and degradation of forest contributes 12% of CO2 emissions and recent analyses suggest that forest conservation could provide up to 40% of cost-effective CO2 mitigation needed through 2030 for a greater than 66% chance of keeping warming to < 2 °C. However, monoculture plantations are not the answer. For forests to do their job now and into the future they themselves need to be resilient to climate change, and this is contingent on being species rich and carefully restored in accordance with the latest science and local knowledge.  A pine monoculture might store carbon now but it is unlikely to be able to continue doing so in a rapidly changing world. Furthermore, afforestation with non-native species may have unintended negative outcomes, such as drought. Evidence is growing that the more diverse a forest, the more resistant it is to disease and the more likely it is to continue converting atmospheric CO2 into plant biomass, even when climatic conditions change.

Don’t forget blue carbon, peatlands and grassland soils
It’s also vital that the emphasis on forests does not detract from other ecosystems, many of which are very important for storing carbon. I am thinking in particular of marine and coastal ecosystems (reefs, mangroves, dunes, salt marshes, seagrass beds) which are increasingly referred to as “blue carbon” owing to their high carbon content. Indeed, marine habitats occupy 0.2% of the ocean surface yet contribute 50% of carbon burial in marine sediments. Mangroves in particular are the planet’s greatest carbon storehouses, with CO2 burial rates  (i.e. rates at which carbon is converted into biomass through photosynthesis) 20 times greater than any other terrestrial ecosystem, including boreal and tropical forests. Habitats such as peatlands and grassland soils also hold vast reservoirs of carbon yet barely feature in climate change policy. We mustn’t prioritise forest at the cost of continuing to destroy—or, heaven forbid, replace—other vitally important ecosystems. So let’s be more inclusive when we talk about nature-based solutions and when we encourage decision makers to take them into account.

100 trillion dollars of ecosystem services, including climate change adaptation
In our excitement to promote forest conservation as a means of reducing emissions and slowing warming, we mustn't overlook the vital role of natural habitats in protecting us from climate change impacts. We know that natural habitats in river catchments secure and regulate water supplies and protect communities from flooding, soil erosion and landslides; that mangroves, reefs and salt marshes to protect us from storm surges, salt water intrusion and erosion; and that agroforestry (planting trees among crops or crops within forest) can maintain and even enhance yields in drier more variable climates. Moreover, there are many economic benefits of these nature-based solutions through avoided losses to climate change related disasters. For example, coastal wetlands in northeast USA protected over 600US$ million worth of property from direct flood damages during Hurricane Sandy, while annual damages from flooding would double and costs from frequent storms would triple in the absence of reefs globally. In other words, planting trees and restoring nature isn’t just about storing carbon and slowing warming, it’s also about protecting ecosystems which in turn protect us from floods, droughts, landslides, storms, heatwaves and other disasters increasingly common under climate change. It is about working with nature in such a way that ecosystems continue providing services for people (clean air and water, timber, pollination, fertile soils, etc.) which according to one study, total over 100 trillion US dollars per year.

So, we should celebrate the rapidly growing recognition of nature’s importance in a warming world. We should welcome the fact that nature-based solutions are finally becoming major discussion points at meetings such as the Climate Action Summit this week. However, as agendas get translated into actions, let us not forget the importance of biodiversity. In the fight against climate change, forests make good allies, but without restoring and protecting biodiverse ecosystems, we cannot win the battle. I hope those negotiating for action and funding in San Francisco this week will bear this in mind.


Learn more: some of the science behind the statements
Beck et al. 2018. The global flood protection savings provided by coral reefs. Nature Communications.
Duarte et al. (2013) The role of coastal plant communities for climate change mitigation and adaptation. Nature Climate Change.
Field & Mach (2017) Rightsizing carbon dioxide removal. Science 356: 706–707.
Griscom et al. (2017) Natural Climate Solutions. PNAS
Hamilton & Friess (2018) Global carbon stocks and potential emissions due to mangrove deforestation from 2000 to 2012 Nature Climate Change
Hanewinkel et al. (2012) Climate change may cause severe loss in the economic value of European forest land. Nature Climate Change 3: 203–207.
Isbell et al (2015) Biodiversity increases the resistance of ecosystem productivity to climate extremes. Nature.
Narayan et al. 2017. The value of coastal wetlands for flood damage reduction in the northeastern USA. Scientific Reports
Warren et al. (2009) Reducing deforestation is essential for constraining global temperatures to 2°C above pre-industrial levels. DOI: 10.1088/1755-1307/6/15/152003
Weismeier et al (2015) Carbon storage capacity of semiarid grassland soils and sequestration potentials in northern China. Global Change Biology.
Yang et al (2015) Ecosystem Evapotranspiration as a Response to Climate and Vegetation Coverage Changes in Northwest Yunnan, China. PLOS One.