What are nature-based solutions to climate change?
Human activity has significantly altered natural environments in all parts of the world and has contributed greatly to the stock of greenhouse gas emissions in the atmosphere: for example, releasing carbon dioxide when felling trees and methane from rice and livestock farming. It has also limited the ability of natural systems to absorb and store, or sequester, carbon from the atmosphere and for natural features such as coral reefs and mangroves to protect communities from the increasingly severe impacts of climate change.
So-called ‘nature-based solutions’ are one part of the response to limiting climate change and will also help address the interlinked crisis of global biodiversity decline.
What shape do these solutions take?
Nature-based solutions to climate change are a collection of approaches that offer the potential to both reduce and remove emissions. They do this by enhancing the ability of ecosystems to sequester carbon dioxide, or reverse the degradation of an ecosystem so that it no longer emits harmful greenhouse gas emissions and once more becomes a ‘net sink’ of carbon (meaning it stores more carbon than it emits).
Nature-based solutions include: avoiding emissions through protecting landscapes to limit deforestation; restoring ecosystems such as drained peatlands so they sequester carbon and improving degraded habitats by bringing ecological diversity into landscapes dominated by singular species; improving management practices of farmed land such that emissions are reduced and sequestration is maximised; allowing waterways to meander along their natural courses to reduce flood risk; and better integrating nature into urban areas and agricultural landscapes.
As well as removing emissions from the atmosphere by sequestering it in plants, soils and sediments, these practices provide a number of other important benefits such as cleaner air and water, flood and erosion control, increased biodiversity, enhanced resilience and ability to adapt to climate change impacts, and even economic benefits borne from a cleaner environment – for example, reductions in healthcare costs associated with cleaner drinking water.
How important are nature-based solutions to climate change mitigation and adaptation?
Nature-based solutions have become increasingly salient in international climate policy and discourse, as evidenced by the fact that 102 nations (or 84% of those that are Parties to the UN Framework Convention on Climate Change) have included nature-based solutions as part of their Nationally Determined Contributions (NDCs), or national emissions reduction plans, submitted as required by the Paris Agreement.
Nature-based solutions are an effective tool for mitigating greenhouse gas emissions but cannot work as a sole response to climate change. Guidance from the Intergovernmental Panel on Climate Change (IPCC) is clear that there is a need for “…deep emissions reductions in all sectors, across a wide portfolio of mitigation options”. Thus, nature-based solutions can be seen as a complementary approach to the deep gross emissions cuts principally made through decarbonising economies by switching to renewable sources of energy and so on (with additional removals made through technological solutions), which all countries and economic sectors will need to achieve.
The scale and speed of carbon removals from nature-based solutions mean that they will contribute a limited amount to efforts to reach net zero by 2050.This is because restoring a degraded ecosystem such as a peatland to a healthy state through re-wetting takes multiple years, and accumulated carbon dioxide removals will only become apparent over a timescale of decades.
However, recent evidence indicates that well designed nature-based solutions can play a powerful role in reducing temperatures over the remainder of the century. A synthesis of available evidence indicates that, under a moderately ambitious scenario, nature-based solutions could avoid or remove up to 10 gigatonnes (Gt) of CO2 equivalent per year up to 2050, with 85% of these saved emissions a result of changed land management practices, such as incorporating agroforestry into conventional agricultural practices. However, emissions savings will likely be substantially lower than this unless widespread incentives to continue emissions-intensive and destructive practices for agricultural expansion such as deforestation are removed. One study finds that cost-effective nature-based solutions can only contribute around 20% of the reductions needed by 2050, with decarbonisation making up the remainder. This evidence indicates that nature-based solutions hold mitigation potential, but they cannot be relied upon alone to meet the 1.5°C target.
Nature-based solutions also have an important part to play in adapting to the impacts of climate change. For example, moves to protect or restore coastal wetlands, mangroves, seagrass, sand dunes and coral reefs are now seen as both effective and economical adaptation measures that help to stabilise shorelines and dissipate wave energy to reduce flooding and erosion. Such natural coastal defence projects have found to be between two and five times more cost-effective than engineered projects. The Global Commission on Adaptation also finds that the benefits of mangrove restoration for fisheries, forestry, recreation and storm or inundation risk reduction exceed costs by a factor of 10.
Criticism of nature-based solutions and principles for good practice
In some cases, nature-based solutions have been employed with a short-sighted focus on rapid CO2 removal without due attention to other environmental implications. For example, in Chile between 1986 and 2011, subsidies and poor regulatory oversight likely led to afforestation that decreased biodiversity without increasing the total carbon stored in above-ground biomass. Similarly, in Cambodia, a 34,000 hectare reforestation project resulted in native forest being replaced by a species monoculture at considerable cost to local biodiversity – and the local community. Indeed, other challenges concern the legacy of projects that have not respected land tenure or existing customary rights of Indigenous peoples or local communities and been developed without their free and informed consent. Nature-based solutions have also been charged as being a form of greenwashing, whereby emitters such as airlines can offset their emissions in a ‘nature-friendly way’ (e.g. by planting trees) while not pursuing overall reductions.
To counteract some of these negative perceptions and damaging uses of nature-based solutions, a consortium of 20 UK-based organisations spanning academic and non-governmental organisations have developed a set of guidelines to nature-based solutions. These have been adopted by the ‘Together With Nature’ campaign, a call to corporate leaders to commit to four principles for investing in nature-based solutions. They include not substituting such solutions for the rapid phase-out of fossil fuels, including Indigenous peoples and local communities in their design and implementation, and ensuring they support or enhance biodiversity.
This explainer has been written by Leo Mercer with the help of Esin Serin, Natalie Pearson and Georgina Kyriacou.