Coastal ecosystems may be the most anthropogenically-altered on the planet.  Habitat loss, over-fishing, nutrient loading, and many other impacts have fundamentally changed the structure and function of these systems.  Many of these impacts operate over rather large spatial scales (think global warming or the loss of migratory fishes); however, most marine ecology actually is conducted at the smallest scales.  Foundational ecological theory took root in experiments conducted in coastal intertidal zones, often at scales of a meter or less.  But ecologists now are challenged to develop approaches that better fit the large scales at which human impacts are altering coastal ecosystems.

In terrestrial systems, “landscape” ecology is a well-developed sub-discipline.  Yet tenets of this are rarely applied in marine systems.  This study was among the first to do so and to use manipulative approaches as we constructed a series of artificial reefs in the Bight and specifically chose locations within different “seascape” contexts.  This allowed us to examine the importance of relatively large-scale (hundreds of meters) features in determining local fish community structure.  That is, instead of just examining small-scale aspects of the reef itself, we included much larger scale factors (such as seagrass cover) and used these to explain the makeup of fish communities.

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We found that the amount of seagrass at large spatial scales was one of the most important features determining to number and identity of fishes using these artificial reefs.  Specifically, reefs that had more seagrass within 100 m had more fishes.  This may be explained by the fact that many reef species like grunts, snapper and lobster that use reefs during the day migrate out into the surrounding seagrass at night to feed.  However, not all species of fish responded to the amount of seagrass in the same way.  For example, the number of white grunts increased with more seagrass cover within the seascape, but the number of French grunts decreased.  This means that changes in the cover of seagrass within large areas surrounding reefs can affect both the number and types of fishes using reefs.  Human activities that cause even subtle changes to seagrass habitat can impact reef fish communities even before the complete loss of seagrass habitat.

Up to 32 percent of the world’s fish stocks are over exploited, depleted or recovering, they warned. Up to half of the worlSee the dozens of unique artificial fish habitat models, fish attractors and fish cover used at fishiding.com, the leader in  science based, proven, fish protection.d’s mangrove forests and a fifth of coral reefs that are fish spawning grounds have been destroyed.

The U.N. Environment Program says less-destructive ways of fishing that use more labor and less energy are needed to help restore the health of the world’s oceans and coasts.

The agency is leading a five-day conference in Manila of experts and officials from 70 governments.

Jacqueline Alder, head of UNEP’s marine, coastal and freshwater office, said the increasing ranks of rich Asians are driving demand for better quality fish that are often not abundant, adding pressure to their supply.

“People don’t want to eat the little anchovies anymore when they can eat a nice snapper or grouper — much nicer fish, shows much more of your wealth,” she told reporters.

Alder said booming population, more awareness of health benefits from eating fish, fuel and boat-building subsidies in industrial fisheries, weak management and limited understanding of ecosystems’ values are also driving fish overexploitation.

AP

She said subidies should be reduced or eliminated, fishing gears should be less destructive, and the number of boats and fishers reduced. Habitat management should also be strengthened and marine protected areas established.

Fish is the main source of protein for up to 20 percent of the of world’s population and some 180 million people are directly or indirectly employed by the fishing industry, she added.

Vincent Sweeney, UNEP’s coordinator for the Global Program of Action to prevent marine environment degradation from land-based pollutants, said up to 90 percent of sewage in developing countries is discharged untreated into rivers, lakes and oceans, posing one of the most serious threats to water resources.

Other pollutants from land including nitrogen and phosphorous from fertilizers and detergents result in hypoxia or “dead zones” where too many nutrients cause an undesirable growth of plants that compete with coral reef and other marine life for oxygen.

Jerker Tamelander, head of UNEP’s coral reef unit, said healthy coral reefs can produce up to 35 tons of fish per square kilometer each year while there is a catch reduction of 67 tons for every square kilometer of clear-cut mangrove forest.

The global market value of marine and coastal resources and industries is estimated at $3 trillion per year or about 5 percent of the global economy, he said. Non-market value such as climate, water, nutrients and carbon regulation is estimated at $22 trillion a year.

“We’ve lost a fifth of the world’s coral reefs and 60 percent are under direct and immediate threat and climate change plays an additional role in driving reef loss,” he said.

Tamelander said the decline in coastal ecosystems’ health and productivity can be reversed by shifting to greener and more sustainable strategies, addressing threats and better management that involves all stakeholders.

“The sooner we act, the easier it will be and the longer we wait the harder it will be,” he warned.