It is no surprise to longtime Hawai'i residents that the state's reefs are in a degraded condition.

If you remember a reef where you could grab a lobster in a foot of water, but no longer; where corals grew colorfully but are now smothered by mud; where clouds of neon fishes swept in and out of the rocks but now don't, then chances are you're pretty old and you've been here a long time.

But someone jumping in the water here for the first time might not recognize that the reefs are in peril.

Australia coral reef scientist Terry Hughes, writing with co-authors in the journal Trends in Ecology and Evolution, makes the point that coral reefs everywhere are in trouble, and that it's mainly because of people. His chilling opening lines:

"The recipe for killing a coral reef is simple: distort food webs from the top down by overharvesting, or from the bottom up by adding nutrients, and add to the mix the stresses of climate change, emergent diseases and a myriad of other anthropogenic impacts."

"Anthropogenic" means caused by people, and Hughes makes the point that people's easy assumptions about how to deal with the issue aren't always useful.

In places, for example, where marine reserves have been established for a long time, among the animals that come back are the predators. How are they different from human fishers? It seems that groupers, moray eels and barracuda take fish in a way that is different from that of humans. For one thing, they tend to take smaller fish and leave bigger ones behind—while humans generally focus on the big ones and leave the small.

In the case of uhu, or parrotfish, these reef inhabitants are important at controlling fleshy seaweeds and thus promoting corals. On reefs protected from fishing, Hughes says, research shows that while there were lots more predators, there also were lots more big parrotfish, so seaweed cover on the reef was significantly less.

Hughes also notes that it can take time for a reef to recover from damage. Research on a series of no-fishing reserves in the Philippines, he wrote, shows that while big predators increased sixfold, the amount of other fish was also steadily increasing—and after two decades of protection, the amount of fish was continuing to rise.

The point, perhaps, is that we can tinker with catch sizes, bag limits and seasons, but it may be that in some cases, the best solution is a simple no-take reserve in which nature does its own management.

If you have a question or concern about the Hawaiian environment, drop a note to Jan TenBruggencate at P.O. Box 524, Lihu'e, HI 96766 or jant@honoluluadvertiser.com. Or call him at (808) 245-3074.