Two studies on the impact of human activity on oceans have returned very contrasting results. The first, published in Science, says that the fauna in the oceans is on the verge of an extinction-level event, though we are not over the brink yet. A team of researchers at the University of California, Santa Barbara, juxtaposed existing and new data from sources as diverse as fossil records to sea-bed mining and fishing vessels to claim that human activity has seriously endangered marine fauna, with potentially devastating consequences for the planet. The second, published in BioScience, authored by a team of marine biologists at the University of Western Australia, Perth, claims that ocean calamities are oversold and a healthy degree of scepticism should be adopted in reacting to such news. This set of researchers found strong evidence for some human activities causing severe ecological disruptions, with over-fishing as a prime example. But for others, the evidence, they say, is equivocal .
All assessment of the oceans’ health are foundationally uncertain because it is much more difficult to track the state of marine species—imagine keeping tabs on, say, particular Sei whales when they travel over hundreds of thousands of kilometres annually—than those on land. Also, there is scientific consensus that changes in some ocean ecosystems may not represent a global trend. At the same time, it is important to recognise that there are changes afoot directly resulting from human activity—nearly 40% of the coral reefs worldwide have died out, the population of many fish and mussels have dwindled beyond a critical threshold, thanks to over-fishing. Our oceans are also carbon sinks—with increasing emissions, waters are turning acidic and their temperatures are rising. Some fish are already migrating to cooler waters where they are not a natural species. Whether or not we are at the throes of an extinction event, it would be better to preempt the risks and preserve ocean ecology.