The Top 5 Causes of Marine Habitat Destruction

Our seas and oceans are the Earth’s most distinguishing feature – even from space. Our planet is 70% ocean, where 94% of our species live[sc:1]. We use our seas and beaches for recreational purposes or to feed us and fuel our economy through fishing and shipping. But there is more beneath the surface. Healthy oceans and seas are paramount to our planet’s health but they are under increasing stress. Studies suggest that[sc:2]:

• 30-35% of critical marine habitats such as seagrasses, mangroves and coral reefs are estimated to have been destroyed.
• There are close to 500 dead zones covering more than 245,000 km² globally, equivalent to the UK’s surface.
• Up to 13% of global fisheries have ‘collapsed’ due to overexploitation of fish stocks.

 Compounding factors such as climate change are making the situation more urgent and there is an increasing need to redress the reasons for marine habitat destruction. Five key reasons our marine habitats are being destructed around the globe are the following:

• Eutrophication

In addition to industrial emissions that end up in seas, rivers or lakes, an important source of habitat destruction for our marine environment is eutrophication. Eutrophication happens when fertilisers are washed off from the land and find their way into our marine environment. The presence of fertilises increases the content of nitrate and phosphate in the water. This in turn accelerates the development of algae which prevents the sun from reaching other water plants – as a result of this, plants perish. This leads to a lack of oxygen which can leave the area lifeless. This phenomenon of marine dead zones was first noted in the 1970’s with one of the largest zones being the Gulf of Mexico.

• Coastal area development

Coastal areas are considered prime locations for both living and going on holidays as well as economic activity. From housing and recreational venues, to marinas and aquaculture, coastal areas have been in many cases “over-developed” to the detriment of local ecosystems and habitats. According to WWF, more than half of the Mediterranean coastline is now urbanized with infrastructure that is a major cause of habitat loss[sc:5]. Offshore developments, such as oil and gas exploration and drilling, are another reason for habitat destruction.

• Shipping

With around 90% of world trade being conducted via shipping[sc:6], it is reasonable to suspect that it is also a major cause of marine habitat destruction. Evidence further supports that as shipping impacts our aquatic environment in several ways and has a disproportionate impact on parts of our seas which are busy shipping lanes and ports.

Beyond air emissions, ships can pollute the marine environment and cause disturbances of those ecosystems by releasing into the water biocides, used in antifouling paints applied to the exterior of ships and through the discharge of garbage and sewage into the sea. Further damage is caused through the dropping of anchors, noise and wave disturbances, and striking of whales and other marine mammals[sc:7]. Additional damage can be caused in the case of a spill or an accident such as the Exxon Valdez case when an oil tanker struck a reef off of Alaska’s Prince William Sound causing gallons of oil to be spread into the water.

• Unsustainable fishing practices

Unsustainable fishing practices are leading to a depletion of our fish stock globally. According to the European Environment Agency, in 2010 30 % of Europe’s commercial fish stocks were being fished beyond safe biological limits whereas 70 % of commercial stocks were fished above maximum sustainable yield[sc:8]. In many parts of the world, subsidies allow more fishermen to operate exacerbating over-fishing which is further compounded by those who do not respect the laws already in place. In addition, fishing techniques such as bottom trawling, create further damage of the seabed and its habitats. In bottom trawling, a large net with heavy weights is dragged across the bottom of the sea catching everything it encounters with many things mistakenly caught and then discarded such as endangered fish or vulnerable deep-sea corals. This can amount up to 90% of a trawl’s total catch[sc:9]. The bottom trawl itself, due to its size and weight, can destroy seafloor habitats that provide aquatic species with sources of nutrition and shelter.

• Inadequate protection

Another reason that our marine habitats continue to be destroyed is that quite simply we have not legislated to protect them. Only 3.4% of the world’s oceans have been designated as protected – compared to almost 16% of our planet’s land area. The percentage drops further when one takes into account that most protected areas suffer from little or no management, almost all are open to tourism and recreation, and 90% are open to fishing activities[sc:1][sc:0].