Marine reserves help fish resist climate change invaders

Southeast Australia is an ocean warming “hotspot” – a region where temperature at the ocean’s surface is increasing more rapidly than elsewhere. That means this part of Australia is like an outdoor laboratory for understanding nature’s response to climate change.

In research published this week in Nature Climate Change, we found that marine reserves in this regional “hotspot” are important in reducing the effects of climate change on different species.

As oceans warm, subtropical species migrate into temperate regions. This creates new communities where groups of species may meet for the first time.

One species that has already extended its range is the spiny sea urchin. This urchin has grazed down the seaweed beds attached to rocky reefs as it has moved southward, leaving a swath of barren patches in its path.

Habitat reserves protected from fishing within marine reserves appear to deter the urchin. Here, predatory lobsters grow to a size where they can feed on incoming urchins. Marine reserves can also give a diverse set of predatory fish the opportunity to develop. These fish may feed on other warm-water migrants, making it harder to colonise the area.

However, unless there is long-term data, it is virtually impossible to understand how biological communities respond to steady increases in temperature as opposed to year-to-year temperature variability.

We need to know which species are present and how their numbers fluctuate through time. Such data are rare, which makes it hard to know whether protection from fishing will lead to healthier ecosystems that have greater resilience (that is, the capacity to resist and recover following a disturbance).

But we do have one useful data set. Over 20 years, information has been collected on the fishes from the Maria Island Marine National Park in Tasmania and nearby sites open to fishing. This allows us to look into the past to understand what has changed.

Read the full article, with full links, The Conversation, here

• The New York Times’ Editorial Board: The value of Marine Reserves

On the face of it, the value of a marine reserve — the equivalent of a national park or wildlife preserve on land — seems obvious. The oceans are in trouble, and setting aside regions of biodiversity, where fishing is strictly limited, if not prohibited, is one of the few effective means of protecting many species at once. But politically, there is nothing simple about creating marine reserves in international waters. Recently, China and Russia succeeded in blocking, yet again, the creation of a large marine reserve in Antarctica.

New research indicates that marine reserves may have an even greater importance than scientists previously supposed. A study recently published in Nature Climate Change found that marine reserves do more than merely shelter species that live within them. By enhancing the resilience of marine communities, reserves help ward off some of the effects of climate change, including invasion by species from warmer waters.

The study was based on research conducted at the Maria Island Marine Reserve, just off the coast of Tasmania. Though the reserve was only established in 1991, data on marine life there had been collected for more than 70 years. Comparing the reserve’s ecosystem with similar but unprotected waters where fishing was allowed, scientists found greater long-term and short-term stability.

The overall health of the ecosystem helped create what the authors of the study called “a feedback mechanism to promote stability.” The scientists found a substantial increase in the number of large-bodied fish and much less fluctuation, year to year, in the population of smaller fish.

This is a reminder of something that all too easily goes unnoticed. How species will endure the effects of global warming depends less on the individual species than the overall health of the ecosystem it belongs to. This study also suggested another essential service that marine reserves provide. By giving us a view into a relatively unaltered past — since the 1940s in the case of Maria Island — they show how healthy ecosystems function, which will be increasingly valuable as climate change disorders them.

The New York Times’ Opinion, here

• Meawnhile, more radical, alternative energy solutions, the Sheerwind, here