美国国家公共电台 NPR Deep Seagrass Bed Could Stall Climate Change, If Climate Change Doesn't Kill It First（在线收听）

Deep Seagrass Bed Could Stall Climate Change, If Climate Change Doesn't Kill It First

MICHEL MARTIN, HOST:

Staying on the subject of climate change for a few more minutes, there was another bright spot this past week amid all the dire warnings we have been hearing about the effects of climate change. And it is a very big bright spot - a meadow of seagrass some 50 feet below the surface off the coast of Australia. It is said to be twice the size of New Jersey, and it's soaking up and storing a lot of carbon that otherwise would contribute to global warming.

Jennifer Howard is director of marine climate change at Conservation International. She has spent years studying so-called carbon sinks, and she's come in to explain the latest discovery. Jennifer Howard, thanks so much for joining us.

JENNIFER HOWARD: Thank you so much.

MARTIN: So, first, I'm going to ask you to walk me through what is a blue carbon sink. And why is it called that?

HOWARD: Sure. So blue carbon sinks really refer to three main ecosystems - seagrass being one of them, of course, then, also, salt marshes and mangrove forests. These ecosystems are powerhouses when it comes to removing carbon out of the atmosphere but, even more importantly, storing it in the soil beneath them. So these coastal blue carbon ecosystems can sequester or remove carbon from the atmosphere about four times the rate of terrestrial forests on land. And they store about 10 times more carbon in the system itself.

MARTIN: How does it work? How does it do what it does?

HOWARD: So seagrasses are just flowering grasses that live underwater. So, like all plants, they remove carbon dioxide from the atmosphere and convert that into the actual plant matter itself so the leaves, the flowers, the roots. And so, then, when those seagrasses die, all of that gets buried underneath. And because of their root system, which is very intricate, it kind of locks it down and holds it in there.

But the unique thing about a blue carbon ecosystem is that saltwater really inhibits bacterial breakdown of that material. So, basically, once the plants die, they're preserved within the soil. And, again, in this study, particularly, these are seagrasses next to the Great Barrier Reef. And having the seagrasses that absorb that CO2 are actually protecting the reefs against ocean acidification degradation.

MARTIN: So is the news, here, that this exists, or is the news here of what these carbon sinks actually can accomplish, can do for us?

HOWARD: Well, you know, the science behind what these systems are and what they can do for us is pretty well-established. The interesting thing about this study, in particular, is that seagrass beds are very hard to find. Because they're underwater, satellite imagery is - it's very difficult to pick them up and find where they are. So you usually have to throw somebody in the water with a scuba mask to go actually find them. So...

MARTIN: Couldn't you invite them, nicely, to go in with a scuba mask?

HOWARD: (Laughter).

MARTIN: You have to throw them in?

HOWARD: We could - I think most people don't mind scuba-diving in...

MARTIN: (Laughter).

HOWARD: ...Tropical locations...

MARTIN: Yeah.

HOWARD: ...For sure, near the Great Barrier Reef.

MARTIN: But this is something that requires some effort to find.

HOWARD: Yeah, absolutely. And, because of that, we just don't know how many of these large patches of seagrasses there actually are out there.

MARTIN: So tell me more about what's amazing. Is it that - is the - how much work is this particular patch? Or can you sort of quantify how much carbon this area is soaking up? Or what do we think it's contributing?

HOWARD: Probably on average. And I haven't done the calculations for this particular patch and its size. But, you know, we think that there's probably about several billion tons of carbon locked away in the seagrass meadows all over the world. And the unique thing about these ecosystems, as well, that I really want to mention is not only are they fantastic for removing carbon from the atmosphere, which makes them important for all climate change mitigation policy, but when you destroy those ecosystems, all that carbon can be rereleased back into the atmosphere.

MARTIN: That was going to be - my question is that - are these deep seagrasses endangered? Is this something that we should be concerned about?

HOWARD: So, again, we don't know that much about deep seagrasses. But, in general, looking globally, seagrasses are being lost at about 2 percent per year, which is very significant. But most of that loss is really coming from poor water quality. What happens when you have pollutants and too much sediment running down the river, it blocks out the light. It buries the seagrass, and they start to die. The solution to that is really going to be land-based. You're going to have to address the pollution component first.

MARTIN: And, finally, do scientists suggest that we should be cultivating seagrass? Is that even a thing? Can that be done?

HOWARD: It can be done. I think, though, that one thing to keep in mind is that seagrasses are very prolific. And so, if they're not currently being seen there, there's a reason why. So if you just go and plant in these areas, it's probably not going to do very well.

MARTIN: That's Jennifer Howard, the marine climate change director at Conservation International. She was commenting on the findings of Peter Macreadie at Deakin University in Australia. Jennifer, thanks so much for talking to us.

HOWARD: Thank you. This was great.