365 Days of Climate Awareness 220 – Human Threats to the Reefs of Indonesia

Coral reefs throughout the world are vulnerable to the impacts of human society and, in particular, global warming. These include warming and acidifying water, outside the tolerance of coral polyps. They include excess sedimentation from nearby land, when forests are cut down and replaced by farms or buildings, which results in increased erosion and added sediment being deposited offshore, which can choke the reefs. It includes overfishing, where segments of the reef population are removed for food, upsetting the entire reef’s biological balance and contributing to their death. But there are some human threats  particular to southeast Asia.

Map of Southeast Asia's Coral Reef Threat Levels

The first is the use of explosives, known as dynamite fishing, blast fishing or fish bombing. (It’s what Crocodile Dundee was doing in New York harbor at the start of Crocodile Dundee II. It’s also known to occur in the Philippines, off the coast of Africa and in the Aegean Sea.) Dynamite works well but is expensive and nearly impossible to obtain. It’s possible to achieve the same goals using explosives made from fuel and fertilizer. The fisherman lights the explosive and tosses it in the water. When it explodes, the pressure wave kills most fish within the vicinity (depending on the size of the charge) by rupturing their swim bladders. The fishermen are then free to harvest and sell the dead fish.

Dynamite fishing.

The catch.

The practice is extremely destructive to all life in the area (including, sometimes, those of the fishermen). The pressure wave kills or wounds most animals, and can badly damage macroscopic algae. The immediate area of the detonation can leave craters in the structure of the reef. Enough blast fishing will kill a reef community. The practice is more common on smaller, hard-to-patrol islands where fishermen can work with near impunity. Local activists trying to end the blast fishing stress that it is not a subsistence practice. Rather, the practice brings significant wealth to the ones who organize it.

The damage.

Cyanide fishing.

Second is cyanide fishing, common in the coral triangle because of the spectacular diversity and appearance of the fish. It is a practice aimed at producing live exotic animals as pets for collectors worldwide. The fisherman swims underwater with a squirt bottle full of cyanide (CN-) solution, and then squirts a cloud of it in the vicinity of the target fish. If done skillfully, the fish is stunned and is easily bagged by the fisherman, live, for later sale and transport. Like blast fishing, cyanide fishing is common in the more remote island coasts of Indonesia, the Philippines and the surrounding islands. As long as there is a wealthy market for exotic fish, and as long as the reefs continue to exist, cyanide fishing is likely to continue.

Tomorrow: Indonesia and global warming.

Be brave, and be well.