Troubled Waters

The rapid loss of marine biodiversity could have dire consequences in the long term. By Rabia Mughal

The biodiversity in the world’s oceans is declining at an accelerated pace, and if the trend continues all fish and seafood species could collapse by the middle of this century, according to a study published in the November 3 issue of the journal Science.

Over the last 200 years the number and diversity of marine animals in coastal systems has eroded—a trend mirrored in the global ocean for the last half century, co-author Heike Lotze of Dalhousie University, said in an email.

The loss of biodiversity is already affecting ocean ecosystems and human welfare, and business as usual will lead to the collapse of marine species by 2048, according to the study. Every species lost spurs the unraveling of the ecosystem. But the scenario isn’t entirely bleak—the international team of ecologists, economists, and fisheries scientists says that restoring species greatly adds to the stability and productivity of the ecosystem and its ability to endure stresses.

Though people might feel the loss of marine life as a major food source most acutely, it’s only one of the negative effects. Impoverished ocean ecosystems can’t filter pollutants, resist diseases, or rebound from stresses such as over fishing and climate change as readily. As a result, human well-being is threatened.

“Human health risks emerge as depleted coastal ecosystems become vulnerable to invasive species, disease outbreaks, and noxious algal blooms,” says Lotze. 

Some people may also feel a pinch in their pocketbooks. Coastal areas are likely to suffer economically as water quality declines.

But not everybody agrees with the study’s projections. “Predicting that all commercial fisheries will be extinct by 2048 is simply silly,” says Daniel Schindler, a fisheries expert at the University of Washington. “[It] remains unclear if it is the biodiversity of marine ecosystems per se that makes certain fisheries more stable, or if this is an artifact of the distribution of fishing effort over global biogeographic patterns for fishes.”

The usual suspects are to blame for this downward spiral, says co-author John  Stachowicz. He points out that some of the major contributing factors to biodiversity loss are the addition of pollutants and nutrients to ecosystems, destruction of habitats, overfishing and climate changes instigated by the excessive release of carbon dioxide into the atmosphere.

Despite the author’s dire predictions, they say there’s still time to reverse the trend. “Trends in protected areas worldwide show that restoration of biodiversity increased productivity four-fold in terms of catch per unit effort and made ecosystems 21 percent less susceptible to environmental and human caused fluctuations on average,” says Lotze. Pollution control, maintenance of essential habitats, creation of marine reserves, and integrated fisheries management are some measures that can turn the situation around, say the authors.