Hawaii has a closing window of opportunity to save our reefs before it’s too late, yet few people are speaking up for our reef saviors. Will you?

Healthy coral reefs provide valuable goods and services for everyone. These natural freebies include productive fisheries, coastal protection from increasing erosion due to rising sea levels and worsening storms, recreational opportunities, breathtaking beauty, spiritual inspiration and new medicines.

Unfortunately, our reefs have been devastated by mud flowing off poorly managed coastal zones and smothering reefs, and by excess fertilizers and leaching wastewaters that stimulate seaweeds to overgrow and outcompete corals. Now, as an ever-warming ocean bleaches and kills more coral, many of our reefs are on the brink of collapse.

Ironically, the one ecological service of healthy reefs that makes them resilient to such assaults — herbivory in scientific jargon — is also the victim of human shortsightedness. By eating seaweeds, parrotfishes (uhu), surgeonfishes (kala, kole, manini and others), chubs (nenue) and other herbivores keep dead coral surfaces clean so new corals can settle, survive and grow. The different species remove different seaweeds in different ways, so it takes a diversity of herbivores to keep a reef clean.

Yet many of these fishes, especially uhu and kala, are terribly overfished near human population centers. For example, around the island of Oahu, total reef herbivore populations are at less than 5% of their estimated unfished abundance.

While large coral colonies can hold their own against encroaching seaweeds, baby corals cannot survive such overgrowth. When coral dies for any reason, the dead coral surfaces will typically become covered by either seaweed or new coral, depending upon the local abundance and diversity of herbivorous fishes and some sea urchins.

Think of a healthy reef as a living, self-reinforcing, positive feedback loop: herbivores control seaweeds, so corals thrive and provide shelter and living space for not only herbivores but all reef life. Kill the corals and remove the herbivores, and the reef ecosystem collapses.

Amazingly, powerful interests — from both the top down (e.g., some politicians) and the bottom up (e.g., some fishermen) — refuse to acknowledge the critical link between healthy herbivore populations and healthy coral reefs. Depletion of herbivores is seen as only a fisheries issue, with managers merely trying to bring populations up to 30% of their unfished abundance. But even if not technically overfished by this narrow-minded definition, reducing herbivore populations by only half may destroy the ability of these living lawnmowers to keep our reefs clean and resilient to coral mortality events.

Coral bleaching caused by ocean warming is worsening rapidly. Scientists predict that Hawaiian coral reefs will bleach every single year by 2040. Reefs with more herbivores and coral are known to resist and recover from bleaching events much more rapidly than degraded reefs.

Hawaii’s corals are presently sitting ducks. With our reefs already stressed by poor coastal water quality, and now increasingly by coral bleaching, the herbivores that could save the day are few to be found along crowded coasts like much of Oahu and Maui.

Is all hope lost? If Hawaii’s luck persists, we might avoid major coral mortality for another decade, and if we act now to replenish herbivore populations, then there is hope.

On Friday, the state Board of Land and Natural Resources (BLNR) will consider new herbivore fishing rules that have been terribly weakened by those who oppose fishing restrictions. It is time for the silent majority of Hawaii to demand an end to the status quo of ignoring the loss of our reef saviors: uhu and friends. Make your wishes known now by emailing the BLNR at blnr.testimony@hawaii.gov.

Mark Hixon is the Hsiao Endowed Professor of Marine Biology in the University of Hawaii-Manoa School of Life Sciences; Alan Friedlander is senior director of research for National Geographic Pristine Seas and an affiliate researcher at the Hawaii Institute of Marine Biology; Randy Kosaki is the research ecologist at the NOAA Papahanaumokuakea Marine National Monument and affiliate graduate faculty of marine biology at UH-Manoa. They advise Fish Pono-Save Our Reefs (fishpono.org).