Sea Levels Rising at Fastest Rate in 3,000 Years
Sea levels in the 20th century rose faster than at any time in the last 3,000 years. And in the 21st century, the tides will climb ever higher—by at least 28 cms (11 inches) and possibly by as much as 130 cms (51 inches), according to two new studies.
Human activity is implicated in both studies and although neither delivers a new conclusion, each represents a new approach to studies of sea level rise as a consequence of climate change and each is a confirmation of previous research.
Robert Kopp, a climate scientist and Earth historian at Rutgers University in the U.S. and colleagues reveal in the Proceedings of the National Academy of Sciences that they tried to look at the greenhouse century—the 100 years in which oil, gas and coal combustion began to change the mix of carbon dioxide in the atmosphere and trigger a rise in planetary average temperatures—in the context of the last 27 centuries.
They compiled a geological database that stretched back to the Bronze Age, which lasted, with regional variations, from the fourth to the first millennium before the Christian era. And they developed a new statistical approach to examine the sea-level indicators retrieved from marshes, coral atolls and archaeological sites around the world.
They report that although sea level rise might have happened without human action, it would have been less than half the observed 20th century increase and might even have fallen.
Had humans not piled greenhouse gases into the atmosphere, more than half the 8,000 coastal floods recorded at U.S. tide gauges in the last century might never have happened. On average, sea levels rose 14 cms between 1900 and 2000.
“The 20th century rise was extraordinary in the context of the last three millennia—and the rise over the last two decades has been even faster,” Dr. Kopp said.
In the same journal, a team led by Matthias Mengel, a postdoctoral researcher at the Potsdam Institute for Climate Impact Research, Germany, report that they took a new look at what might happen to sea levels before 2100.
They modeled three scenarios for greenhouse gas emissions, incorporated the latest 20th-century data on melting glaciers and warming oceans and played with the mathematical approach in a new way to predict a set of outcomes.
The most hopeful—based on the agreement by 195 nations last December at the UN climate change conference in Paris—led to a projected increase of between 28 and 56 cms. The most alarming outcome proposed a possible range of sea level rise from 57 to 131 cms.
The two studies are designed to give practical information to city authorities and coastal planners.
Even a 60 cm rise means nations will have to think about coastal protection.
“With all the greenhouse gases we have already emitted, we cannot stop the seas from rising altogether, but we can substantially limit the rate of the rise by ending the use of fossil fuels,” said Co-Author Anders Levermann, a professor of climate system dynamics who is based both at Potsdam and at Columbia University’s Lamont-Doherty Earth Observatory in the U.S.
“This is quite a challenge, but less expensive than adaptation to unabated sea level rise, which in some regions is impossible,” Prof. Levermann said. “If the world wants to avoid the greatest losses and damage, it now has to rapidly follow the path laid out by the UN climate summit in Paris a few weeks ago.”
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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>
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