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Diving Deeper: Health of Coral Reefs

Episode 54 (December 5, 2013)

HOST: Beautiful, colorful, calm, and serene. These words may come to mind when we see amazing images of a diver underwater surrounded by coral reefs, but these incredible resources have faced and continue to face many threats.

Here to talk to us today on Diving Deeper is John Christensen, the director for NOAA's Coral Reef Conservation Program. John will help us explore the health of coral reefs, the threats facing our reefs, and hopefully some actions that we can take to do our part in protecting these important resources. Hi John, welcome to our show today.

JOHN CHRISTENSEN: Thanks for inviting me here today Kate. It's always been a pleasure to step away from the hustle and bustle to talk about the many values of coral reef ecosystems and what NOAA's doing with its many partners to conserve these majestic places.

HOST: Well, John, to start off, what can you tell us about the overall health of our coral reef ecosystems?

JOHN CHRISTENSEN: Well Kate, on balance, experts agree across the globe that coral reef ecosystems are in peril. As with most things in nature, healthy, intact ecosystems are a delicate balance of the physical environment, their biological inhabitants like fish and turtles and mammals and corals among many others, and the people who interact with these systems. As each of these elements change in relation to one another by definition, the very ecosystem itself also changes. Over the past several decades, the net result of these changes has been an overall decline in the condition of reefs globally.

HOST: So would you say then, and maybe you just touched on this, are we declining, improving, or staying about the same from where we were say 10 years ago?

JOHN CHRISTENSEN: As I've just mentioned, coral reefs have been in a state of general decline over the past several decades including over the last 10 years. We see this expressed in the health, abundance, and diversity of the coral reefs themselves and the animals that depend on healthy coral.

HOST: And before we get into the threats that our reefs face and the impacts of these threats to the overall health of our coral reefs, can you remind our listeners, why are corals so important to us?

JOHN CHRISTENSEN: Coral reefs provide an incredibly wide range of benefits. What usually jumps to people's minds is that coral reefs are a bastion of biological diversity often called the rainforests of the sea. Covering less than one percent of the ocean floor, reefs support an estimated 25 percent of all marine life with over 4,000 species of fish alone. So, corals provide habitat, its home to over one million different aquatic species. It provides income for people, billions of dollars and millions of jobs in over 100 countries around the world depend on coral reef ecosystems. Of course, part of that is food, food for people living near coral reefs, especially in small island nations. It also provides protection, coral reefs are actually a natural barrier protecting coastal cities, communities, and beaches from storms. And what most people don't think about, but equally important, is the potential use in medicine. Extracts from corals are used in treatments for many of the world's most prevalent and dangerous illnesses and diseases.

HOST: OK, so we can't argue with that. They're very valuable to us, to everybody, anywhere that you are. So John, let's get right into this and the topic of our podcast today. What are some of the threats facing our coral reefs today?

JOHN CHRISTENSEN: While there are many threats that face coral reefs today, the NOAA Coral Reef Conservation Program tends to focus on three key issues. That includes land-based sources of pollution, the impacts of fishing, and climate change on these ecosystems.

HOST: So, let's take these one by one from the list of threats that you just mentioned and talk about these a little bit more. First—pollution. What kinds of pollutants are entering, and how are they entering, waters around coral reefs?

JOHN CHRISTENSEN: Pollution from land-based sources is a cause of coral reef decline throughout the world. In the Caribbean for example, about 80 percent of ocean pollution originates from activities on land. As populations expand in coastal areas and develop, it alters the landscape, increasing the runoff from land, so this runoff often carries large quantities of sediment from land clearing for example, high levels of nutrients from agricultural areas and sewage outflows, and pollutants such as petroleum products and pesticides.

HOST: And what can happen to a reef when the water around it becomes polluted?

JOHN CHRISTENSEN: Well, going through the list that I just mentioned, excess nutrients for example, results in poor water quality, leading to enhanced algal growth on reefs, which crowds out corals and significantly degrades the ecosystem. In addition, sediment deposited onto the reef can smother corals and interferes with their ability to feed and to reproduce. And finally, pesticides for example, can interfere with coral reproduction and growth. Sewage discharge and runoff may also introduce diseases into coral reef ecosystems.

HOST: So, we'll come back and talk about that threat again in just a few minutes, but let's go next up to fishing impacts. Can you tell us how this is a threat to our coral reefs?

JOHN CHRISTENSEN: Yeah, you know fishing impacts actually can be seen in a number of ways and tends to be actually fairly complicated, but as I think about it in more simple terms, you can have mechanical impacts, that is, things like fish traps breaking reefs or a trawl scouring the bottom. There's population level impacts—if you fish in a place and you extract all the fish, suddenly they're all gone and the ecosystem therefore is impacted. And then the ecosystem level impacts so this is where it all comes together and for example, you might have a fish which usually grazes on the reef and keeps it clean of algae and so forth, well, if they're removed from the reef, suddenly the reef becomes impacted more and more by this algae that we talked about. So there's a number of ways which fishing can impact coral reef ecosystems.

HOST: John, probably the one threat that we've heard the most about is climate change. How does climate change threaten coral reefs?

JOHN CHRISTENSEN: Well, climate change impacts have been identified as one of the greatest global threats to coral reef ecosystems. As temperatures rise, bleaching and infectious disease outbreaks are likely to become more frequent. Additionally, carbon dioxide, absorbed into the ocean from the atmosphere has already begun to alter the sea water chemistry through changes in pH or ocean acidification. This change can actually dissolve reef skeletons.

HOST: So from these three main threats to coral reefs—pollution, fishing impacts, and climate change. Are one of these three having a greater impact on our reefs or does this vary based on your geographic location?

JOHN CHRISTENSEN: All of these things come together at varying degrees depending on your geographic location. So the truth is that one of these probably plays a more predominant role depending on where you're at. Also of note though is the global effect of climate change is ever present no matter where you're at. So if you were to ask me to answer which is truly always omnipresent, I would say that climate change is there and we are able then to address the other threats more strategically on the ground.

HOST: And John, what is the role of NOAA's Coral Reef Conservation Program in all of this that we've been talking about today?

JOHN CHRISTENSEN: Well, actually the Coral Reef Conservation Program plays a central role in all of this. Not only do we bring together the great community of scientists and managers here at NOAA to work on common issues related to coral reef conservation, but we also serve as sort of the center-piece to bring the federal family together to work on issues that are much greater than just what NOAA alone can work on. A big piece of that is actually the relationship that we have with the states and the territories, with universities, with non-governmental organizations, so truly the entire conservation community comes together, and that's one of the roles that we play is convening all of these people with common purpose and cause.

We all address together some of the issues that we talked about—climate for sure being one on everybody's plate and pollution of course, fishing as well.

HOST: John, from what you've told us so far today, I think most of us would like to know what, if anything, we can do to help?

JOHN CHRISTENSEN: Well, even if you don't live near a coral reef, you can help protect coral reefs in the United States and around the world. There are lots of actions, little and big, that you can take in life to help conserve a coral reef. If every household, for example, in the U.S. replaced a burned out bulb with an energy-efficient EnergyStar qualified fluorescent bulb, it would prevent greenhouse gas emissions equivalent to that from at least 800,000 cars. That's 800,000! So climate change is clearly one of the leading threats of coral reefs.

Educate yourself about coral reefs. So what we're doing here today is incredibly important. Understand not only what a coral reef is itself, but the animals that they support. How many different species live in reefs, what new medicines have been developed from reef organisms. Participate in training and educational programs that focus on ecology. When you further your own education, you can help others understand the fragility and value of the world's reefs and that awareness is actually key to conservation across the globe, coral reef or not.

Another example is to be an informed fish tank owner. Only buy marine fish and other reef organisms when you know they've been collected in an ecologically-sound manner. Don't release store-bought fish into local waterways and ask store managers where these organisms came from, for example.

HOST: Well, that's quite a list of things we can do and things we can do which is really important to know, it's not just if you live close to a coral reef. John, my last question for you today, is just to see if you have any final, closing words for our listeners?

JOHN CHRISTENSEN: Yes. I'd actually like to take the opportunity to say that even though coral reef ecosystems face these incredible threats, that I have great optimism. That together as a community across the globe, we can protect and preserve coral reef ecosystems for future generations.

HOST: Thanks John for joining us today on Diving Deeper to share some of the threats facing our coral reefs and what we can all do to help. To learn more, visit

That's all for today's show—thanks for tuning in. Diving Deeper will take a break until the new year. See you all again in 2014!