Science Briefs

Cartoon diagram of mangrove swamp interactions

U.N. Report Spotlights Need to Strengthen Climate Change Adaptation

A report recently issued by the United Nations Environment Programme documents how most countries have adopted climate adaptation into their policy and planning, but how well they are doing so is a mixed picture. Cynthia Rosenzweig and Manishka De Mel of the NASA Goddard Institute for Space Studies (GISS) and Columbia University's Center for Climate Systems Research are among the lead authors of the Adaptation Gap Report 2020, which was released on Jan. 14, 2021.

While strong action to reduce greenhouse gases is essential, adaptation is needed more than ever. 2020 was not only the year of the pandemic; it was tied with 2016 as the warmest year on record according an analysis by NASA GISS. The warming climate brought devastating impacts across the world: floods, droughts, storms, wildfires and locust plagues.

Even more worrying is that the world is heading for at least a 3°C temperature rise this century, based on current pledges under the Paris Agreement. This will only intensify these impacts. The Paris Agreement requires all its signatories to plan and implement adaptation measures. The new UN report finds that adaptation action is lagging far behind. While nations have advanced in planning and implementation, huge gaps remain, particularly in finance for developing countries.

Just 5% of climate finance is allocated for adaptation ($30 billion of $579 billion per year). Annual adaptation costs in developing countries alone are estimated at $70 billion currently. This figure is expected to reach $140-300 billion in 2030 and $280-500 billion in 2050. Both public and private finance for adaptation must be urgently stepped up, along with faster implementation.

The report has a special focus on nature-based solutions (NbS) — actions such as restoring mangroves for coastal protection. Using nature to adapt to climate change can improve human well-being and conserve biodiversity benefits. Scaling up nature-based solutions will be particularly critical to help meet the goals of the Paris agreement.

There has been a marked increase in implementation of NbS for adaptation over the past two decades, but it is unclear whether this trend will continue. New initiatives with NbS for adaptation have risen from a handful in 2000 to over 70 per year today (not counting urban NbS). Despite encouraging trends, the scale of adaptation progress at the national level is insufficient and tracking progress remains a challenge. A review of NbS project databases revealed the major hazards being addressed and NbS being utilized to address these (see Figure 1). Intense precipitation is addressed by about a third of initiatives, followed by drought (8%), rising temperatures (17%) and coastal storms (12%). These hazards are being addressed through the protection, restoration, implementation or management of forests and other landscapes; rivers, floodplains and peatlands; and urban green and blue spaces; and green infrastructure.

Complex diagram connecting underlying hazards to their impacts on the ground and how different NbS are being used to address them

Figure 1. Sankey diagram connecting underlying hazards to their impacts on the ground (proximate hazards) and how different NbS are being used to address them. (Credit: Adaptation Gap Report 2020)

National and international policy and actions are increasingly recognizing that NbS play a vital role in climate change adaptation. Over 50% of countries (> 90% of Least Developed Countries) have added elements of NbS to the adaptation components of their Nationally Determined Contributions (NDCs). But most countries only describe broad goals and less than one third describe measurable targets. NbS for adaptation are often low-cost options that bring environmental, economic and social benefits to a wide range of stakeholders, including women and poor and marginalized groups.

The substantial impacts of high-end climate change on biodiversity can limit the effectiveness of NbS and increase societal vulnerability thus reducing adaptation choices. Potential biodiversity impacts under low- and high-end climate scenarios are highlighted in Table 1. Climate mitigation has to work in tandem with adaptation. Adaptation needs to ramp up since climate change is upon us. A 1°C increase of global surface temperature rise has resulted in record temperatures and increasing extreme events across the world. Nature-based solutions are an essential component of a portfolio of adaptation approaches that can be used to enhance resilience. At the same time they help communities and countries respond to climate change and protect the environment.

Low-end climate scenarios High-end climate scenarios

• Risks to natural and human systems are expected to be lower at 1.5°C than at 2°C of global warming (high confidence), as lower rates of change help maintain the ability of natural and human systems to adapt.

• Terrestrial and wetland ecosystems and the services they provide will suffer less if warming is limited to 1.5°C, rather than to 2°C, with the percentage of terrestrial land area projected to be affected by ecosystem transformations standing at 13 per cent at 2°C and approximately 4 per cent at 1.5°C.

• Large-scale changes are observed in ocean ecosystems, with critical thresholds expected to be reached at 1.5°C.

• Warming towards 1.5°C will see increases in water temperatures that are expected to drive some species (such as plankton and fish) to migrate to higher latitudes and cause novel ecosystems to assemble. Species that are less able to relocate (e.g. corals) are projected to experience high rates of mortality and loss.

• Risks to ecosystems in oceans include declining ocean productivity, shifts of species to higher latitudes, ecosystem damage (such as to coral reefs and mangroves), loss of productivity in fisheries, and changes to ocean chemistry (for example, acidification).

• High-end scenarios project an increased risk of global extinctions — the fraction of species at risk of climate- related extinction is 5 per cent at 2°C warming, rising to 16 per cent at 4.3°C warming.

• Although the adaptive capacity of ecosystems and species is substantial, many will neither be able to cope with increased extreme events and variability, nor adapt to the projected high rates and magnitudes of climate change. This will ultimately result in their loss, along with the services they provide to people.

• Species with long generation times show limited adaptive capacity at high rates of climate change, due to the inherent adaptive capacities of many species being exceeded.

• Under high magnitudes of climate change, species with restricted populations (for example, in isolated habitats or on mountain tops) are expected to undergo adverse effects, reducing their abundance, resilience and viability.

• Terrestrial and freshwater ecosystems are at risk of abrupt and irreversible regional-scale change in their composition, structure and function under large magnitudes and high rates of climate change.

Table 1. Examples of potential biodiversity impacts under low- and high-end climate scenarios (Credit: Adaptation Gap Report 2020)

Of the fraction of climate finance that is diverted to adaptation, only a small proportion is targeted towards NbS for adaptation. Cumulative investment for climate change mitigation and adaptation projects under four major funds stood at $94 billion. However, only $12 billion of this funding was spent on nature-based solutions. The NbS finance base for adaptation could be strengthened by deploying innovative mechanisms that combine public and private sources of funding. This analysis suggested that support for green initiatives with some element of NbS has risen over the last two decades, although not enough.

Closing the finance gap for nature-based solutions is an urgently needed to protect communities, the environment and the economy. Market-based approaches and the private sector can play a pivotal role in mobilizing investments in NbS. Relying on grants and development funding alone is insufficient. Payments for ecosystem services, climate bonds and insurance products are innovative approaches that all have the potential to scale up NbS.

The potential of NbS for adaptation can best be fully realized by limiting the risks of dangerous levels of warming and by scaling up ambition and action on protecting, conserving and restoring nature. During the COVID-19 pandemic climate change has fallen down the political agenda at all levels of governance. COVID-19 stimulus packages present an opportunity to raise ambition and could lead to climate-resilient and low-emission recovery.

Please address all inquiries about this research to Dr. Cynthia Rosenzweig.

+ Return to Science Briefs

+ Return to News & Features