Protecting Mangroves Can Prevent Billions of Dollars in Global Flooding Damage Every Year
Hurricanes and tropical storms are estimated to cost the U.S. economy more than $50 billion yearly in damage from winds and flooding. And as these storms travel across the Atlantic, they also ravage many Caribbean nations.
We study coastal ecosystems and how to value the natural coastal defenses provided by mangroves, marshes and coral reefs. In a new study, we map flood risks along more than 435,000 miles (700,000 kilometers) of subtropical shoreline in 59 countries around the world.
Along these coasts, we calculate that flood risks exceed $730 billion annually in direct impacts to property. Many government agencies and insurers estimate that indirect impacts to livelihoods and other economic activity are two to three times these direct flood costs.
We also estimate that across these 59 countries, mangroves – salt-tolerant trees that grow along tropical coastlines worldwide – reduce risk to more than 15 million people and prevent more than $65 billion in property damages every year. Mangroves do this by blocking storm surge – the rise in sea level during storms – and dampening waves, which protect people and structures near the shore.
Tropical storms are a well-recognized hazard along many coasts. In 2019, which was an above-normal year for tropical storm activity, 90 named storms formed around the world, including 62 days with major tropical cyclones.
As one example, Hurricane Dorian devastated the northern Bahamas with sustained winds of some 185 miles per hour. Throughout its life, Dorian's path impacted more than 17 nations and 15 U.S. states and territories, from Grenada to Newfoundland.
And Dorian was not even the strongest cyclone of the year. That title went to Super Typhoon Halong in the Western Pacific, which steered clear of land. Many scientists predict that climate change will make these storms more intense, with a likely increase in the proportion of storms that reach Categories 4 and 5.
It would be logical to assume that countries map the flood risks from these storms, since they have to protect residents who live near coasts, along with public infrastructure such as ports, airports, wastewater treatment centers and power plants. These facilities often are built in low-lying areas around urban and suburban centers.
However, governments and businesses only develop flood risk analyses for the shorelines of highly developed nations, where people have the resources to pay for or insure against these risks. This excludes most tropical countries, where many of the world's most vulnerable people live.
Tropical storm tracks since 1842. NOAA
Our study was designed to quantify these flood risks worldwide and identify solutions for reducing them. We used tools that are standard in the insurance and engineering industries, along with a five-step approach for calculating expected damage, to develop high-resolution estimates of flood risk globally. Then we coupled spatially explicit hydrodynamic flood models with economics to estimate impacts to people and property.
We focused on mangroves because they are large trees that grow quickly in salt water at the edge of the coastal zone, where they form a front line of defense. Mangroves are also excellent at trapping sediments and building land. On average, land around mangroves grows vertically by 1 to 10 millimeters per year.
We generated maps summarizing the benefits that mangroves provide in 20-kilometer coastal units around the world. They show that there are 100 coastal areas where mangroves avert $100 million or more in property damages every year. These are clearly priority zones where mangrove conservation and restoration will yield highly cost-effective benefits to people, property and national budgets.
According to our estimates, the U.S., China and Taiwan receive the greatest economic benefits – protection of property – from mangroves. Vietnam, India and Bangladesh receive the greatest social benefits – protection of people.
Along some 20-kilometer coastal stretches, mangroves provide up to $500,000,000 in flood reduction benefits yearly. Michael Beck, CC BY-ND
Mangroves as Green Infrastructure
Mangrove destruction has been widespread, largely because of coastal development and aquaculture. From 1980 through the early 2000s, the world lost up to 20% of existing mangrove habitat. The rate of loss has slowed but still continues, driven by urban expansion, pollution and agriculture.
Given our findings about how valuable mangroves are for coastal protection, we believe they should be viewed as national infrastructure and made eligible for funding from hazard mitigation and disaster recovery budgets, just like other coastal defense structures. Paying for mangrove restoration can work through the same approaches that are currently used to fund engineered protective structures such as seawalls.
Several new studies done collaboratively with Risk Management Solutions, a leading insurance risk modeling firm, show that coastal marshes and mangroves provide significant storm reduction benefits. These findings could underpin the development of innovative insurance options for natural systems.
Examples are already being developed for coral reefs in Mexico and across the Caribbean. Conserving mangroves where they occur together with coral reefs can multiply the flood protection benefits from habitats.
Working with the World Bank, countries like the Philippines and Jamaica are assessing how the benefits of mangroves can be incorporated into national finances, disaster management and proposals for the U.N. Green Climate Fund, which was created in 2010 to help developing countries mitigate greenhouse gas emissions and adapt to climate change. Our work was supported by the World Bank and Germany's International Climate Initiative to help inform solutions for nations that are most at risk.
In many places, preserving and restoring mangrove forests can be an extremely economically effective strategy for protecting coasts from tropical storm damage. As national governments and insurers grapple with disaster management costs that are growing nearly exponentially worldwide, we believe our research can create new opportunities to pay for mangrove conservation and restoration using climate adaptation, disaster risk reduction and insurance funds.
Reposted with permission from The Conversation.
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By D. André Green II
One of nature's epic events is underway: Monarch butterflies' fall migration. Departing from all across the United States and Canada, the butterflies travel up to 2,500 miles to cluster at the same locations in Mexico or along the Pacific Coast where their great-grandparents spent the previous winter.
Millions of People Care About Monarchs<p>I will never forget the sights and sounds the first time I visited monarchs' overwintering sites in Mexico. Our guide pointed in the distance to what looked like hanging branches covered with dead leaves. But then I saw the leaves flash orange every so often, revealing what were actually thousands of tightly packed butterflies. The monarchs made their most striking sounds in the Sun, when they burst from the trees in massive fluttering plumes or landed on the ground in the tussle of mating.</p><p>Decades of educational outreach by teachers, researchers and hobbyists has cultivated a generation of monarch admirers who want to help preserve this phenomenon. This global network has helped restore not only monarchs' summer breeding habitat by planting milkweed, but also general pollinator habitat by planting nectaring flowers across North America.</p><p>Scientists have calculated that restoring the monarch population to a stable level of about 120 million butterflies will require <a href="https://doi.org/10.1111/icad.12198" target="_blank">planting 1.6 billion new milkweed stems</a>. And they need them fast. This is too large a target to achieve through grassroots efforts alone. A <a href="https://www.fws.gov/savethemonarch/CCAA.html" target="_blank" rel="noopener noreferrer">new plan</a>, announced in the spring of 2020, is designed to help fill the gap.</p>
Pros and Cons of Regulation<p>The top-down strategy for saving monarchs gained energy in 2014, when the U.S. Fish and Wildlife Service <a href="https://www.fws.gov/southeast/pdf/petition/monarch.pdf" target="_blank">proposed</a> listing them as threatened under the Endangered Species Act. A decision is expected in December 2020.</p><p>Listing a species as endangered or threatened <a href="https://www.fws.gov/endangered/esa-library/pdf/listing.pdf" target="_blank">triggers restrictions</a> on "taking" (hunting, collecting or killing), transporting or selling it, and on activities that negatively affect its habitat. Listing monarchs would impose restrictions on landowners in areas where monarchs are found, over vast swaths of land in the U.S.</p><p>In my opinion, this is not a reason to avoid a listing. However, a "threatened" listing might inadvertently threaten one of the best conservation tools that we have: public education.</p><p>It would severely restrict common practices, such as rearing monarchs in classrooms and back yards, as well as scientific research. Anyone who wants to take monarchs and milkweed for these purposes would have to apply for special permits. But these efforts have had a multigenerational educational impact, and they should be protected. Few public campaigns have been more successful at raising awareness of conservation issues.</p>
<span style="display:block;position:relative;padding-top:56.25%;" class="rm-shortcode" data-rm-shortcode-id="91165203d4ec0efc30e4632a00fdf57d"><iframe lazy-loadable="true" src="https://www.youtube.com/embed/KilPRvjbMrA?rel=0" width="100%" height="auto" frameborder="0" scrolling="no" style="position:absolute;top:0;left:0;width:100%;height:100%;"></iframe></span>
The Rescue Attempt<p>To preempt the need for this kind of regulation, the U.S. Fish and Wildlife Service approved a <a href="https://www.fws.gov/savethemonarch/pdfs/Monarch%20CCAA-CCA%20Public%20Comment%20Documents/Monarch-Nationwide_CCAA-CCA_Draft.pdf" target="_blank">Nationwide Candidate Conservation Agreement for Monarch Butterflies</a>. Under this plan, "rights-of-way" landowners – energy and transportation companies and private owners – commit to restoring and creating millions of acres of pollinator habitat that have been decimated by land development and herbicide use in the past half-century.</p><p>The agreement was spearheaded by the <a href="http://rightofway.erc.uic.edu/" target="_blank">Rights-of-Way Habitat Working Group</a>, a collaboration between the University of Illinois Chicago's <a href="https://erc.uic.edu/" target="_blank" rel="noopener noreferrer">Energy Resources Center</a>, the Fish and Wildlife Service and over 40 organizations from the energy and transportation sectors. These sectors control "rights-of-way" corridors such as lands near power lines, oil pipelines, railroad tracks and interstates, all valuable to monarch habitat restoration.</p><p>Under the plan, partners voluntarily agree to commit a percentage of their land to host protected monarch habitat. In exchange, general operations on their land that might directly harm monarchs or destroy milkweed will not be subject to the enhanced regulation of the Endangered Species Act – protection that would last for 25 years if monarchs are listed as threatened. The agreement is expected to create up to 2.3 million acres of new protected habitat, which ideally would avoid the need for a "threatened" listing.</p>
A Model for Collaboration<p>This agreement could be one of the few specific interventions that is big enough to allow researchers to quantify its impact on the size of the monarch population. Even if the agreement produces only 20% of its 2.3 million acre goal, this would still yield nearly half a million acres of new protected habitat. This would provide a powerful test of the role of declining breeding and nectaring habitat compared to other challenges to monarchs, such as climate change or pollution.</p><p>Scientists hope that data from this agreement will be made publicly available, like projects in the <a href="https://www.fws.gov/savethemonarch/MCD.html" target="_blank">Monarch Conservation Database</a>, which has tracked smaller on-the-ground conservation efforts since 2014. With this information we can continue to develop powerful new models with better accuracy for determining how different habitat factors, such as the number of milkweed stems or nectaring flowers on a landscape scale, affect the monarch population.</p><p>North America's monarch butterfly migration is one of the most awe-inspiring feats in the natural world. If this rescue plan succeeds, it could become a model for bridging different interests to achieve a common conservation goal.</p>
The annual Ig Nobel prizes were awarded Thursday by the science humor magazine Annals of Improbable Research for scientific experiments that seem somewhat absurd, but are also thought-provoking. This was the 30th year the awards have been presented, but the first time they were not presented at Harvard University. Instead, they were delivered in a 75-minute pre-recorded ceremony.