Contact Us

Destroying the marine habitat

30 November, 1999

Sean Mc Donagh writes about dangers to the marine habitat.

In my previous article entitled Fish are becoming scarce I looked at how we are currently over-fishing the oceans. The deep sea habitat is also under threat from the crude and destructive methods of fishing that are so often used.  For a start the nets are huge and usually weighted down with heavy bolts. As they are dragged along the bottom of the ocean they rip everything in their paths and scoop up everything from the sea bed. These include corals and sponges and some of these are hundreds of years old. The final result is a totally destroyed marine environment that took hundreds of years to develop. Since none of this material has a commercial value for the fishermen it is simple dumped back into the ocean as bycatch.

A New Zealand marine scientist interviewed by Martha Holmes on the BBC series The Blue Planet explained that the best way for us land creatures to understand the destructive nature of deep sea fishing is to compare it with a similar way of getting food on land.  If we took our cue from the fishermen in order to get some beef we would first hire a helicopter. Then we would trawl a huge net across the countryside. This process would capture a cow, the primary target of our endeavour. With the  cow would come the dog, the car, the barnyard door, the farmer’s wife and a whole lot of things we did not wish to get in the first place. Once the nets were wenched in we would discard everything except the cow.  Though it sounds implausible and outrageous, this is not as destructive as our methods of deep sea fishing. These are tearing apart ecosystems that are 700 years old, that are the equivalent of the topical forests in terms of richness of species, and leaving behind devastation.  Unfortunately the wreckage is out of sight and for most of us it is not our concern.

Coral Reefs
Shallow water habitats are also under threat. Coral reefs are the tropical forests of the oceans. Many have developed over hundreds of years and are replete with a extraordinary array of marine life. The wonderful structure of the corals themselves provides animals and fish with a safe habitat in which to breed and to feed. During my 20 years in the Philippines in the 1970s and 1980s I spent many hours snorkeling around reefs. I came to love the magic of coral reefs, their magnificent architecture and the pastel colours of the reef fish as they dash in and out of the coral cover.  Corals are truly a wonderland. They are also the nursery for many species of fish.

Today many reefs are being fished out for luxury fish like groupers and humphead wrasse. The problems is that these are being fished out at an unsustainable level.  Martha Holmes discovered that a staggering 30,000 tonnes of reef fish passed through Hong Kong each year in the late 1990s. As stocks in reefs in nearby countries are depleted fishing boats have to seek out new coral reefs, often 3,000 miles away.  Marine biologists are worried that much of the catch is now composed of juveniles. You do not need to be a marine biologist to realise that when the bulk of your catch are juveniles the end is in sight for that species.  Harvesting fish at a critical point in the life cycle before they can reproduce jeopardizes the future of the species.  It is killing the goose that lays the golden egg!

Mangrove forests are another ecosystem in the shallow oceans that are under threat today. Mangrove forests unfortunately often do not have a good press. All that people see is their twisted root systems, insects and especially mosquitoes. They emit unpleasant odours so that many people, especially in urban areas,  are happy to see them being destroyed and replaced with fish ponds and tourist hotels.

In truth the destruction of mangroves is a tragedy for the earth and the poor. Like the coral reefs they are an extraordinarily productive life system. They provide food and security for young fish.  When these fish have matured they move out to the reefs and wider oceans. Over the past 30 years millions of hectares of mangroves have been destroyed in Asian countries.  Thailand has lost 27 percent of its mangrove cover, Malaysia 20 percent, Indonesia 40 percent and the Philippines 45 percent.  Much of this destruction has happened to make way for shrimp farming and hotels.  Mangroves also protect coastlines from storms and typhoons.  Those areas around the Indian ocean where corals and mangroves were intact and in good shape suffered less from the effects of the 2004 Saint Stephen’s Day earthquake and tsunami. Instead of allowing these wonderful life systems to be destroyed governments and communities should be doing all in their power to protect and restore coral reefs and mangrove forests.