One of the most typical characteristics of reefs in Hawai'i is that they're silent. Wherever you visit a reef in other parts of the world, you can hear parrotfish scraping away at the reef, keeping it clean from algae that would otherwise overgrow and kill corals, eventually causing the whole reef and all organisms that depend on it to collapse.

The collapse of a whole reef ecosystem is not an apocalyptic doom scenario. It has actually happened in many places, especially in the Caribbean.

While the workings of reef ecosystems are not well known and differ from one place to another, many have observed how seemingly small changes to them can have profound effects. The adding of an invasive species or the removal of what scientists call "ecosystem engineers" (such as parrotfish and corals) will inevitably cause some form of reef meltdown.

Some people require actual proof on how this dynamic will play itself out, and when such proof cannot be delivered the scenario described above is deemed to be unlikely. These are the people who are scratching their heads right now in the Caribbean. They realize, too late, that desiring actual proof in a situation where common sense could have worked just as well has cost them dearly.

Needless to say, the costs associated with reef recovery greatly exceed the money earned from depleting these resources in the first place.

I wonder whether Hawai'i is about to make the same mistake.

Many who have been in the Islands for more than 10 years talk about the lower number of uhu that swarm the reef, making it increasingly more difficult to keep a reef healthy in a natural way. Keeping excessive algal and microbial growth under control is a task that we, as humans, will never be able to take over after herbivorous fish and corals have disappeared.

Algal problems in various places in Hawai'i indicate that control of algae by herbivores, such as parrotfish, is already breaking down. The subsequent decline in reef health comes with unnatural changes in microbial communities, and the prevalence of staph infections these days should be regarded as another common-sense indicator that reefs are changing in a direction from which no one will or can benefit.

An obvious way to contribute to the prevention of these problems would be to leave the parrotfish to their work, keeping the reef healthy and for us to enjoy.

Certainly, one should not stop old fishing traditions — but I want to stress the word "old." Semi-industrial fishing for parrotfish on the Islands' north shores, where thousands of pounds of parrotfish are taken using unsportsmanlike collection methods (i.e. spear fishing using scuba gear at night when parrotfish are sleeping), does not remind me of the old days when people took only what they needed.

I am not in a position to judge or tell people what to do, but I do want to point out that the reef decline that has been observed will certainly not become easier to reverse if such practices continue. One doesn't have to be a scientist to understand how this works or see the benefits of a conservative approach when it comes to protecting the foundation that supports Hawai'i's tourism and traditional fisheries on which the income of many depends.

Will the excessive taking of parrotfish be the straw that breaks the camel's back and the last stressor needed to ensure a rapid collapse of Hawaiian reefs? It has certainly happened elsewhere.

Efforts by local fishermen to protect these fishes deserve support. They probably know best how the number of parrotfish has gone down over the last decades.

Local efforts have taken the form of a bill (HB 3260) to limit the taking of parrotfish. I suggest we follow this insight. It would be naive not to trust those who know best and to make the same mistake made in so many other tropical locations that have faced these issues in the past. They did not act, and it has cost them dearly in an ecological, economic and cultural sense.

Mark J.A. Vermeij is a researcher with the CARMABI Foundation in Netherlands Antilles and with the botany department at the University of Hawai'i. He wrote this commentary for The Advertiser.