Defenders of Wildlife Blog

Daniel Thornhill, Coral Reef Marine Scientist

©Richard Ling

Whether it’s polar bears losing their icy habitats in the Arctic or corals bleaching in the tropics, climate change has drastically disrupted the lives of wildlife throughout the world. As our global climate continues to warm, wildlife species will respond with a “MAAD” set of options. Some will Move to a new home where conditions are less stressful. Others will adjust the way they live to Acclimate to the new conditions. Across generations, wildlife populations may even Adapt to the changing planet through natural selection. Too often when these responses are not an option, wildlife will Die as a result of climate change.

These changes are already happening on coral reefs. Reefs are home to more species than any other marine habitat on our planet, but this diverse environment is incredibly fragile. Reef-building corals — the very foundation of these shallow ocean ecosystems — are a delicate partnership between the coral polyps and microscopic algae. When temperatures become too hot, this partnership falls apart — a problem known as coral bleaching. Bleaching causes corals to starve, sicken and eventually die. This has already caused massive die-offs of corals throughout the world, leading the National Oceanic and Atmospheric Administration to propose 66 species of corals as threatened with extinction under the Endangered Species Act.

Despite this grim forecast, death is not the only option for corals. Recently, my colleagues and I investigated how corals respond to climate change. One of our findings is that average yearly temperature determined the northern limits of a coral’s range; if temperatures were too cold, corals could not grow. This is a bit of good news for corals — as warm temperatures push coral reefs away from the equator, many coral species will be able to shift north (or south in the Southern Hemisphere) from one generation to the next. Of course, other conditions must be right in order for this to happen. There must be enough light for the corals’ microscopic algae to thrive, hard surfaces for corals to attach themselves to, currents to move coral offspring to new places, and enough of the dissolved components of seawater that corals need to build their skeletons.

©Toby Hudson

We will need to take action on many levels to address climate change, from lowering greenhouse gas emissions  to planning ahead for a warmer world. Determining where wildlife can live helps us understand both how animals will naturally respond to climate change, and how we can give them the best chance at survival in an era of rising temperatures. Our study is an initial step in understanding these responses in corals.

Coral reefs are huge, immobile structures, but the corals that build them aren’t so static from one generation to the next. If we take action on climate change and learn what reefs need to survive, we can protect corals for generations to come.

by Daniel Thornhill

Ever gone to Google maps and used the “street view” feature to check out a new restaurant?  Or to see which side of the road an address was on?  Well, get ready to use Google maps in a whole new way.  Now you can view some of the most beautiful underwater landscapes on Earth, see fish species you never knew existed, and catch sea turtles napping amid beautiful corals.

Google has launched a new virtual photo tour of the Great Barrier Reef, one of the Seven Wonders of the World and the largest coral reef on the planet, as well as reefs in Hawaii and the Philippines.  The images were gathered for the Caitlin Seaview Survey, a global study of ocean and coral reef health.  There are currently 15,000 images, and by the time the mapping project ends in December, there’ll be about 50,000 available to view!

It used to be that only researchers like me had the opportunity to view and learn about so many different coral habitats and the species that depend on them.  Not anymore: now anyone with an internet connection can go to Google maps for an up-close and personal look at reef life in a growing collection of 360-degree panoramas. This is an unprecedented opportunity for conservation organizations like Defenders of Wildlife, to bring coral reef issues to the fore.

This reef at Dry Tortugas in the Florida Keys includes many different coral species and supports a myriad of fish, invertebrates and other animals. Photo courtesy of the National Park Service.

As a coral reef biologist, I’ve often needed to present the problems reefs face in an engaging way.  Visually documenting reefs is crucial to connecting them to the public.  While national parks and forests are accessible to everyone, coral reefs usually can only be seen in person by scuba divers.  The photos of the Great Barrier Reef and others are a “time-capsule” of the reef’s health.  Coral advocates can use them to educate people around the world, hopefully inspiring them to learn and care about coral reefs.

And coral conservation is more important than ever: climate change, pollution and other stressors are taking a toll on our planet’s reefs, as shown in these incredible “then and now” shots from Double Exposure, a photography site dedicated to showing how climate change alters our environment.  All too often, coral gardens that were vibrant and thriving 20 or 30 years ago are now pale and sparse.  Images are attention-grabbers, drawing viewers in and prompting the questions we researchers ask through our work every day: “how did this happen?” and “how can it be stopped?”

United States reefs in particular are suffering from major issues like overfishing, climate change, and nutrient pollution, which occurs when excess nutrients from waste water or agricultural runoff cause out-of-control algae growth, turning reefs into fields of seaweeds.  I saw first-hand how extreme frigid water temperatures in the winter of 2010 decimated reefs in the Florida Keys, killing corals that had survived for 300 years.  Lionfish, an invasive species that has made its way to the Atlantic coast, voraciously gobble reef-dwelling fish vital to coral ecosystems.  And the international coral trade for aquariums and curios has degraded reefs around the world, including our own.

The challenges that face our coral reefs are great.  But this project is a valuable new gateway to raising awareness about the plight of global coral reefs, and educating the public about how to stop the damage.

Defenders conservation scientist Dan Thornhill was the lead author of a study examining the effects of climate change on coral reefs in the Florida Keys last year- you can read it here.

by Haley McKey

When you think of climate change, you think of more heat waves and droughts, extreme weather, and melting ice caps.  But there’s another problem caused by carbon dioxide emissions, one which is less familiar to us, but no less catastrophic for our planet: ocean acidification.

How it happens:

Carbon dioxide (or CO₂, its chemical formula) is released by the burning of fossil fuels and the clearing of forests and natural areas.  Most CO₂ goes into the earth’s atmosphere, but some is absorbed by our oceans; in fact, about a quarter of the carbon dioxide emitted every year.  That comes to at least 5 million tons of CO₂ absorbed every day.

Algae and marine plants take up some of this CO₂ for photosynthesis, just as land plants do.  But a large amount of CO₂ simply dissolves into surface seawater.  This is what causes ocean acidification.  When CO₂ in the air is absorbed by the ocean, it bonds with water to form carbonic acid, the same stuff that gives an acidic bite to carbonated water and soda pop.  Like all acids, it releases positively charged hydrogen atoms, leaving behind the bicarbonate ion. The problem is that many marine creatures make their shells from a substance with a slightly different chemical composition – calcium carbonate – and the bicarbonate formed by the extra acidity is useless at best, and downright dangerous at worst.

Crustaceans like this sargassum crab need calcium carbonate to fortify their shells. Photo credit David S. Lee

How it threatens wildlife:

When the oceans have more bicarbonate and less carbonate, this interferes with the healthy growth of a variety of organisms, like mollusks (oysters and clams) and crustaceans (crabs, shrimp, lobsters and tiny krill, which are very important to the whole marine food web).  Mollusks take in calcium carbonate, a molecule in ocean water, and excrete it over their bodies to form hard, protective shells.  Crustaceans also use calcium carbonate to fortify their exoskeletons.  But human activities have increased the acidity of the ocean by almost 30% making it more difficult it is for these creatures to create their natural armor. Even tiny zooplankton, the building blocks of marine food chains, need calcium carbonate and cannot grow properly in acidic seawater.

Coral reefs may be in even more trouble.  Corals secrete calcium carbonate skeletons over their bodies to protect them, just like mollusks and crustaceans do.  Ocean acidification can cause corals to grow more slowly, and it is estimated that at current rates of increasing acidity, corals will no longer be able to lay down skeletons by 2150.

 Profound Effects:

The animals directly harmed by acidification may be small, but the effects are far-flung.  Baleen whales like the endangered Atlantic right whale depend on krill and plankton as a food source.  We humans have built whole economies around shellfish, not to mention the hundreds of fish species we eat that depend on them for food, too.  And as coral reefs die, the diverse and unique ecosystems they support can collapse.

Ocean acidification pulls the rug out from under marine food chains and coastal economies.  The only way to stop it is to make serious cuts to carbon emissions worldwide.  If not, it won’t be long before species begin to disappear and many ocean systems collapse completely in their absence.