On mangroves, tsunamis and the genesis of a research project

Ecosystems, such as mangroves on coastlines, or forests on steep slopes can buffer impacts from hazard events and provide other benefits, such as biodiversity and human well-being. Decision-makers are increasingly interested in green solutions for protecting populations, but what is the evidence?

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It started six years ago over lunch in Singapore. Well, really, it started with the Indian Ocean tsunami in 2004. The world’s attention was focused on this tragic event that took the lives of over 200,000 people, one of the most fatal disasters in modern history. Scientists, governments and non-profit organizations were trying to understand how this type of disaster could be prevented in the future. In the aftermath, there was anecdotal evidence from the field that mangroves, coral reefs and sand dunes had reduced tsunami wave intensity in some coastal areas. In the years that followed, mangroves were being planted anywhere and everywhere, not always with proper scientific backing or adequate community inputs.

Sri Lanka, 2009
Figure 1. Development at Yala National Park, Sri Lanka. Left: a resort protected by a healthy, natural dune system.  Right: a resort with dunes removed for better sea view and subsequently destroyed by the 2004 Indian Ocean tsunami.  Credit:.B.G.McAdoo, Sri Lanka, 2009

This was the beginning of a new field of study and policy-making: ecosystem-based disaster risk reduction (Eco-DRR), which falls under the Nature-based Solutions umbrella term. The bottom line is that healthy ecosystems, such as sand dunes, mangroves, coral reefs and seagrasses can buffer certain types of hazards along coasts; vegetation cover on steep slopes can reduce landslides, rockfall and avalanches; forests and vegetation can be managed to reduce wildfires and certain types of flooding events. Yet, the evidence base remained to be mapped out and 28 scientists – many affiliated with the Partnership for Environment and Disaster Risk Reduction (PEDRR) – were determined to document this evidence.

Back to that lunch in Singapore. As I was munching my salad, we decided to start an extensive literature review on this topic, not realizing the long journey ahead: six years of work coordinating 28 co-authors from 16 time zones, two rounds of submissions to Nature Sustainability, weeding through thousands of papers, reviewing hundreds of papers in-depth and collating a large data set. But with resounding confidence, it was all worth it.

Today we are extremely proud to be sharing our newly published paper with you: Scientific evidence for ecosystem-based disaster risk reduction

Review process nuts and bolts

STEP 1: Focus, focus, focus. We started by narrowing our focus: we honed in on English-language peer reviewed papers published during the period 2000-2019. We focused on nine thematic groups of papers related to ecosystems and hazards: coastal, urban, mountain, rivers and wetlands, dryland areas, vegetation and forests, agroecosystems and two cross-cutting themes examining, firstly, the economics of Eco-DRR and, secondly, multiple ecosystems and hazards. You can read the detailed justification for our choices and methodology in our paper.

STEP 2: Form your research team. The project started with a small group of students from Yale NUS-Campus, Singapore and interns at the United Nations Environment Programme (UNEP), Geneva but we quickly realized the need for topic experts to peer review papers. This recruitment may have been the easiest part following years of collaborative work on Eco-DRR through the PEDRR network since 2008. By now, we were one year into our research.

STEP 3: Get your protocol straight, really straight! Inspired by the Intergovernmental Panel on Climate Change (IPCC) review method, we modified our protocol to quantify confidence levels. Each paper was reviewed and “noted” according to two parameters: robustness of evidence and level of agreement (or non-agreement) regarding ecosystems contributing to reducing the impacts of hazards. 

STEP 4: Refine the protocol and start over. After an initial search following our keywords and research protocol, we realized it required some refining. We hit the “reset” button and started again, thanks to research assistants at United Nations University - Institute of Environment and Human Security (UNU-EHS), TH Cologne - University of Applied Sciences, Germany and University of Massachusetts-Amherst, USA. More experts were recruited to create teams of at least two specialists per thematic group. They reviewed and scored papers following a template, with results being discussed, agreed upon, collated and analyzed. By now we were four years into our project.

STEP 5: Draft, redraft, submit and review some more. Results were tabulated, analyzed, drafted, re-drafted and submitted; after receiving reviewers’ comments, we reanalyzed, redrafted and resubmitted. And voilà, a quick recap on the art of good teamwork and persistence paying off six years later. 

Davos, Switzerland, 2018

Figure 2. Protection forest, Davos, Switzerland. Credit: K Sudmeier-Rieux, 2018

Results and next steps

Here is a quick sum-up of results: the economics thematic group recorded the most evidence, dominated by high levels of cost-effectiveness; second was the role of vegetation in reducing mountain hazards and managing fire; third came urban ecosystem-approaches to stormwater flooding issues; in the mid-range were papers on rivers/wetlands and coastal ecosystems, a result influenced by their dependence on numerous factors; the least amount of evidence was provided by papers examining the role of ecosystems in drylands and agroecosystems. A strong cross-cutting theme was the number of co-benefits of all ecosystems beyond protection from hazards (e.g., biodiversity, food and well-being). Unsurprisingly, we found that most research was conducted in North America and Europe, highlighting that the areas most affected by hazard events (e.g., the Global South) need more of this type of research. 

Next steps: two decades of research analyzed over six years left us with a number of questions: we know there is evidence that most ecosystems reduce the impacts of hazard events in a cost-effective manner. Now we need to disseminate this evidence in the language that decision-makers speak: how much, how high, how wide? We also need to focus our attention on performance standards, green design blueprints, ecological engineering standard operating procedures and the specs that will provide the ultimate evidence base to draw attention and investment to nature’s solutions to increasing numbers of hazard events worldwide. Our research in this growing field has only just begun.

For additional information on this topic:

Massive Open Online Course:  Nature-based Solutions for Disaster and Climate Resilience 

- a free online course until 30 November, 2021, developed by PEDRR partners and UNEP

Partnership for Environment and Disaster Risk Reduction; knowledge products and educational resources

Karen Sudmeier

Senior Adviser, Disaster Risk Reduction, United Nations Environment Programme