Hope for Coral Reefs in Crisis

Candice Gaukel Andrews August 11, 2020 0
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Coral reefs provide ecosystem services. If we are to preserve them and their benefits, we’ll need some fresh perspectives on their conservation from the scientific community.

For almost 24 million years, say scientists, coral reefs have functioned relatively unchanged. That is, until the 1980s.

Starting in that decade, tropical coral reef coverage around the world has declined by about 30 to 50 percent. Habitat destruction, overfishing, pollution and people’s use of sunscreens have been among the culprits in many places; but increasingly, coral reef loss can be attributed to climate change. Rising water temperatures are increasing the frequency of mass bleaching events and are making disease outbreaks more common. And as ocean waters become more acidic from absorbing carbon dioxide, it will become harder for corals to grow and maintain their skeletons.

This loss of coral reefs will have serious costs for humans, because many communities depend on reefs for fishing, coastal protection and tourism. What you’ll be able to eat in the future depends, in part, on them. And coral reefs absorb energy from waves that pass over them, buffering shore communities against destructive storms.

Now, coral reef experts are calling for an urgent reevaluation of our climate goals in the light of increasing evidence of the unprecedented speed of change currently happening to these fragile ecosystems. That, coupled with some exciting new findings regarding the adaptability and resiliency of corals, makes me think there is a lot of light at the end of this “underwater” tunnel.

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The absorption of atmospheric CO2 by the world’s oceans contributes to chemical reactions, which ultimately reduce the amount of carbonate available to corals for building their skeletons.

Changing corals and creative concepts

In a special feature in the June 2019 issue of the science journal Functional Ecology, some of the world’s leading coral reef experts addressed how we should define what comprises a functioning coral reef in the Anthropocene—an era where humans are the dominant force of planetary change—among other issues.

As the world’s climate changes, tropical temperatures are shifting toward the poles. As corals are lost to warming oceans in some places and growing in previously inhospitable, cooler waters in others, the rules of how coral reefs function, their species configurations, their geographic distributions and the benefits derived from them by people are all changing, too.

If we are to preserve coral ecosystems along with the benefits and services that they provide, this fluctuating coral reef picture is going to require some fresh responses from the scientific community.

Luckily, many innovative ideas are coming in.

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The widespread loss of corals has spurred a far-reaching effort to save them and to promote their growth.

Many methods and a mix of mindsets

In a 2019 consensus study report titled A Decision Framework for Interventions to Increase the Persistence and Resilience of Coral Reefs, researchers described 23 new ways in which we can improve corals’ persistence in a changing climate. It’s possible to use some of these methods now, such as pre-exposing corals to mild warming in order to improve their tolerance for greater heat levels or replanting reefs. Others may be available for use in the next two to five years, such as using antibiotics to treat coral diseases, mixing cool water into reef habitats, or shading corals from sunlight and heat. Still other proposed interventions—for example, using tools such as CRISPR-Cas9 to genetically manipulate corals to make them more threat-resistant—need significantly more development and research, and are at least a decade away.

Whether a specific intervention is suitable depends, of course, not just on its technical readiness but on each particular ecological and social setting. Local factors such as the level of reef degradation, the quality of the water, and the infrastructure and resources available will determine if a remedy will be beneficial or needed.

Equally important is whether the intervention is acceptable to a community. Engaging a broad set of stakeholders is important for success, as another study demonstrates.

The Fiddle Garden coral reef in Egypt is a favorite site for divers. Its main features are two, large coral pinnacles, one of which is covered in soft-whites and the other in various colors. ©Matt Kieffer, flickr

Critical communications and community commitments

A study published in the May 2019 science journal Nature Communications concluded that when fishers communicate with their rivals and cooperate on local environmental problems, they can improve the quality and quantity of the fish on coral reefs.

In this investigation, researchers interviewed 648 fishers and gathered underwater visual data of reef conditions across five, coral-reef fishing communities in Kenya. They found that in the places where fishers communicated with their competitors about the fishing gear they use, fishing rules and their hunting locations, there were more fish in the sea—and of higher quality.

To have healthy coral reefs, therefore, communication is critical. Developing sustained commitments—such as agreements on rules and setting up conflict-resolution mechanisms—are key to the local management of reefs.

This helpful study even advances a framework that can be applied to other complex problems where healthy environmental conditions depend on the relationships between nature and people.

Colorful parrotfish spend about 90 percent of their days eating algae off coral reefs. This almost-constant activity performs the essential task of cleaning the reefs, which helps the corals stay healthy and thriving. ©Kenneth Lu, flickr

Problem-solver parrotfish and population protections

It seems that even nature itself is giving us hope for the future of coral reefs.

In some recent field studies of two reef ecosystems that are 5,000 miles apart—one in the Pacific and the other in the Indian Ocean—scientists from the Institute of Marine Science in Australia made a surprising discovery: parrotfish flourish in the wake of severe coral bleaching, the blight caused by prolonged exposure to higher sea-surface temperatures.

When bleaching reduces coral cover on the reefs, it creates large areas of newly barren surfaces that are colonized by microorganisms. This provides abundant food for the colorful parrotfish, who use their beaklike teeth to scrape the microorganisms off, cleaning the corals. Writing in the science journal Global Change Biology, the researchers reported that parrotfish numbers increase as much as eightfold on damaged reefs, and the individual fish are about 20 percent larger than those in unbleached areas. More parrotfish suppress the spread of the algae—which hinder the growth of corals—helping to clear the way for reef regeneration.

As a reef begins to return to health, the scientists note, parrotfish populations tend to decline, keeping the ecosystem in balance.

Grappling with greenhouse gases and guiding growth

Other inventive work is underway, too, such as learning more about the molecular mechanisms between corals and the dinoflagellate algae living inside them.

While in the end we’re going to have to grapple with and solve the foremost problem of greenhouse gas emissions, the wealth of intervention options currently and soon-to-be available gives us hope that we’ll be able to help coral reefs successfully survive for now and into the next 24 million years as the beautiful, diverse and productive places that they have always been.

Here’s to finding your true places and natural habitats,

Candy

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