Dual approach needed to save sinking cities and bleaching corals

Dual approach needed to save sinking cities and bleaching corals
Coral bleaching at Lizard Island, Australia, March 2016. Credit: The Ocean Agency / XL Catlin Seaview Survey / Richard Vevers

Local conservation can boost the climate resilience of coastal ecosystems, species and cities and buy them precious time in their fight against sea-level rise, ocean acidification and warming temperatures, a new paper by scientists at Duke University and Fudan University suggests.

The peer-reviewed paper, published Oct. 7 in Current Biology, comes at a time when scientists are divided on whether to continue investing in local efforts to protect threatened places and populations or shift much of that investment toward global efforts to reduce fossil fuel emissions.

"The answer is, you need both," said Brian R. Silliman, Rachel Carson Associate Professor of Marine Conservation Biology at Duke's Nicholas School of the Environment.

"Our analysis of local conservation efforts shows that in all but extreme situations, these interventions significantly buffer the and can buy our sinking cities and bleaching corals time to adapt until the beneficial impacts of global emissions reductions kick in," Silliman said.

In the Florida Keys, for instance, local efforts to cull populations of coral-eating snails reduced thermal bleaching on corals by 40% compared to bleaching on non-treated corals during a three-month spike in water temperatures in 2014. It also promoted faster recoveries.

In Chesapeake Bay, seagrass beds that were wiped out by warming waters and heavy pollution are now reappearing, largely due to local efforts to cut nutrient pollution flowing into the bay.

In Shanghai, where the weight of thousands of high-rises and the depletion of groundwater aquifers causes the ground to sink further each year as the sea is rising, efforts to pump water back into wells and place tighter controls on groundwater use have slowed the subsidence though, and given city officials time to enact other protective measures.

"A common thread in many of the most successful scenarios we reviewed is that the local actions increased climate resilience by removing or reducing human-related stresses that were compounding climate stresses and increasing a species' or site's vulnerability," said Qiang He, professor of coastal ecology at Fudan University in Shanghai, China, who co-authored the new paper with Silliman.

Understanding how human and climate stresses interact is critical for predicting when, where or if local interventions are likely to be effective and what their limits might be, so we can target our efforts accordingly and begin adaptive measures while there is still time, He said.

This is especially true in areas with high human population densities.

One of the most telling examples of this is the tragedy now facing the Indonesian capital of Jakarta, where massive groundwater withdrawal and the weight of 10 million people and their buildings is causing the city to sink by roughly 25 centimeters a year, He noted. By 2050, 95% of the city will be submerged as a result of the compounding effects of and human actions.

"Because Jakarta—unlike Shanghai—did not decrease its human impacts through local conservation or adaptation, the government's only recourse now is to move the entire to a new, higher location on the island of Borneo," Silliman said.

"Unfortunately, other massive migrations of cities inland will become more and more common in coming decades, but we can reduce their number and how quickly they have to happen if we take dual action now on the local and global fronts," Silliman said. "For certain, this is no time to scale back on local conservation. We need to increase our investment at all scales."

Explore further

Local interventions boost coral's resilience to bleaching

More information: Qiang He et al, Climate Change, Human Impacts, and Coastal Ecosystems in the Anthropocene, Current Biology (2019). DOI: 10.1016/j.cub.2019.08.042
Provided by Duke University
Citation: Dual approach needed to save sinking cities and bleaching corals (2019, October 7) retrieved 17 October 2019 from https://phys.org/news/2019-10-dual-approach-cities-corals.html
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Oct 07, 2019

3.1 mm per year since 1993

Oct 07, 2019
The potential for sea level rise is enormous. This is because the ice caps - Greenland and Antarctic - contain huge amounts of fresh water - around 70% of all the freshwater on Earth. If the Greenland ice sheet was to melt away to, sea levels would rise around 6 metres. To put that a different way, a loss of just one per cent of the Greenland ice cap would result in a sea level rise of 6cm.

If the West Antarctic Ice Sheet (WAIS) were to melt, this would add around 6 metres to sea levels. If the East Antarctic Ice Sheet (EAIS) were to melt as well, seas would rise by around 70 metres.

Sea level rise by 2100 is betweem 80cm and 1 metre. Longer term, sea levels will continue to rise even after emissions have been reduced or eliminated.

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