By 2048 All Current Fish, Seafood Species Projected to Collapse
In a study published in the journal Science (3 November), an international collaboration of ecologists and economists shows that the loss of biodiversity is profoundly reducing the ocean?s ability to produce seafood, resist diseases, filter pollutants, and rebound from stresses such as over-fishing and climate change. Boris Worm, the lead author of the study, answers Scitizen?s questions.
What was your goal with this study?
Our goal was to understand how the loss of ocean species is impacting human well-being. Specifically, how the things we take from the ocean, how the various uses we have for the ocean (fishing, tourism, sustainable seafood), these kinds of things, are impacted by the loss of species and what the consequences would be on a global scale.
In your report  you state that at this point 29% of fish and seafood species have collapsed, that is, their catch has declined by 90%, and that all fish and seafood species are projected to collapse by 2048. What’s happening?
We are fishing very hard and we’re collapsing species, meaning that the catch we can get out of these species is declining by 90% or more. Right now, if we look at the global fisheries record—which is all species, in all areas, including all the shellfish, mussels, and fish, meaning everything you can think of that humans consume from the ocean—we have depleted about 1/3 of the resources that are there. You can think of it as a bank account that has a certain amount of money in it and you’ve lost about 1/3 of it and you have 2/3 to go. However, the last third that is there is being drawn from more quickly. What is left is actually an accelerated trend that is projected to lead to a complete collapse in about 40 years or 50 years, at the most.
What are the implications of this loss of biodiversity?
The implications are that humans will suffer because of the loss of these species in various ways. There will be no viable fisheries for wild seafood anymore, which may not be such a problem in countries like ours where we can replace these sources of food, but other countries, particularly developing countries, really feel this loss today and will feel it even more strongly in the future. Then we also found that the quality of the water and the ability of the water to clean itself from toxins, excess nutrients, and also invasive species, is lost when you lose species. The overall productivity of the ocean and the stability of the ocean ecosystem, overtime, are going down based on the available data.
How did you come to this conclusion? What was your process?
We assembled all of the available data sets into four different components. We looked at this problem from four different angles so that we could be very sure that what we would find would be general, that it wouldn’t just apply to one data source. One angle was we assembled all the experiments that people have been doing, seeing whether, exponentially, we have changed the number of species in the ecosystem in the ocean and whether we have looked at the consequences of this. The second one was a historical study of the last 1000 years of history in 12 coastal regions worldwide; these are regions like the Adriatic, the Mediterranean, the Southern North Sea, the Baltic Sea, these are the European areas; then we had one in Australia_ and a larger number of areas in the U.S. and Canada.
Surprisingly, we found that the loss of species had been going on for hundreds of years. It’s not something that’s only been happening recently, but it has definitely been going much faster recently. Also, it is accelerating on a global scale. To look at the global scale, we combined all the fisheries and catch records for all species, for all areas around the globe from the last 50 years and looked at the trends of the dying species there.
Figure: Cantherhines dumerilii. Credit: D.R. Robertson
We also looked at how quickly things were collapsing and how quickly they were recovering in areas that have different species diversity. Remember, we are looking at the impacts of biodiversity loss, so the question is whether or not areas that have a lot of species to begin with may be more robust or may recover faster than those that begin with fewer species. Indeed, we found that the areas that had many species had fewer collapses and faster recovery time, on average, than those with less species.
Finally, we asked how good the chances for recovery are, as well as how easy is it to bring back species, associated productivity, and stability of the ecosystem. We looked at all the places on Earth where people have protected an ecosystem from fishing and looked at the recovery of biodiversity, productivity, and stability in 48 areas worldwide. We found, on average, that species were recovering relatively quickly and also the associated ecosystem services were recovering relatively quickly, within say, 5 or 10 years. That told us, despite the damage being done, there is still substantial recovery potential in the ability of the system to self-repair. What we see in areas that have been degraded too much is that the ability to self-replenish and self-repair is gradually being lost.
How would we go about approaching the reversal of these negative effects?
There is a number of things to do. First of all, we must start seeing the ecosystem as a whole and doing what is called ecosystem management, which is to look at the various impacts we have—not just from fishing, but also from pollution, from the destruction of habitats and so on—then to try to reverse on every one of these fronts.
First and foremost, we have to be smarter about what we take from the ocean, how much we take, how we take it, and how selective we are about taking things from the ocean. We should only take those things that can replenish quickly; fish species like herring and mackerel rebound quickly from over-fishing, whereas others like deep sea species almost never recover; sharks, also, are very very slow to recover. We have to be very careful about these species because they may be lost quickly from the ecosystem, whereas others can replenish.
We have to reduce negative impacts on habitats. A lot of fishing practices destroy the habitats that are essential for the ability of the system to recover; trawling or dragging is the prime example.
Finally, there is still too much pollution. Particularly pollution which clog the ecosystems up with garbage, debris, and excess nutrients which cause problems.
Are you optimistic?
I am a great optimist! When we’ve seen a problem in the past, environmental problems—think of ozone depletion, acid rain, DDT and pesticides—that have become apparent with the consequences visible to everybody, we were pretty smart and quick about turning things around. Not within a year, but within 5 or 10 years. I trust that we can do the same with the ocean. If we hadn’t have done it earlier, we wouldn’t have whales anymore, or tigers or rhinos or elephants anymore. We actually have the power to protect these things and we’re pretty good at it—once we realize what we’re about to lose. I think that what becomes very visible in this paper is that if this trend is to continue, we know exactly where we’re going to end up, for it is very very predictable. I think based on this, I can be optimistic. Once we know the consequences, we will be able to turn things around because we know we don’t want to end up where we’re going to end up if this trend continues.
 Worms et al., Science, 3 November (2006)
Boris Worm works at the Department of Biology at Dalhousie University.
Interview by Thanh Tam Candice Vu and Gilles Prigent