The Ocean

As the human population continues to increase at dramatic rates, fisheries have suffered from the effects of overexploitation. Fish and fish products have provided the global population with a major source of protein for hundreds of years. Within the last several decades the hunt for food in the world's oceans has produced a plethora of fishing techniques that have made fishermen of all varieties, from subsistence farmers to fishermen working in large corporations, highly effective at finding fish. Depending on the environment and scale of fishery, these techniques vary from simple nets spanning a few feet to 'long lines' with thousands of hooks that stretch for miles across the ocean.

Poor policies, governance, and management of this increased fishing pressure has resulted in over-harvesting, which threatens the sustainability of fishing. Targeted species are not the only ones at risk. While most fishing techniques such as long-lining and trawling target specific fish, they often capture other unintended species. These untargeted catches are defined as bycatch. Many fishing methods, including bottom trawling, cyanide poisoning, and blast fishing, also damage marine habitats. On a large scale, bycatch and damage to marine habitats can and has significantly reduced species populations, thus threatening their survival.

Oil and gas exploration and development are ongoing activities fueled by the human population's dependence on fossil fuels. Mining operations both on land and in the sea are driven by the increasing global demand of natural resources. Energy acquisition has the potential to damage marine biodiversity through seismic exploration, equipment construction, ongoing operations and waste disposal. Impacts can include disturbance to sediment, benthic fauna and other seabed flora and fauna, disturbance to marine mammals and other species; loss/destruction of seabed habitat; and effects on water quality.

Climate change will have dramatic effects on the world's oceans. Globally, the changes in atmospheric conditions are being accompanied by changes in sea level, ocean temperature, ocean current systems, biologically important ocean features such as upwelling, and is impacting the basic chemistry of the oceans. These changes will have serious implications for marine biodiversity and natural resources around the world - changing both the basic characteristics of the marine environment and the vital mechanisms that deliver nutrients and transport larvae, thereby sustaining thousands of species of marine life and hundreds of millions of human throughout the world.

IN DEPTH: Learn more about the effects of climate change on the ocean »

With more than half of the world's population living within 60 km of a coastline, Earth's coastal areas are facing pressures never experienced before. Stresses continue to increase, due in large part to human activity such as development, pollution and habitat alteration and destruction, as well as and natural environmental stresses such as climate change. Increasingly, world governments are directing their attention to these geographical areas in an attempt to regulate mankind's effects on the coasts.

The flow of products during international trade and travel may carry more than its intended cargo. The traffic of people and products many times brings unwanted guests along, best known as invasive species. Movement by air and sea typically serve as pathways, or vectors, for different marine species to invade new habitats. Introduction of new species to marine communities can cause imbalances that not only deteriorate environmental integrity but also endanger the survival of endemic and currently threatened species.

Pollution comes in a variety of forms, and from a multitude of sources, and it all has had detrimental effects on the world's oceans. From well known sources such as disastrous oil spills like the 2010 Gulf of Mexico BP oil spill, to the lesser known (and many times more harmful in the long-term) sources like pollutant land runoff which affects ecological processes, public health and social commercial use of marine resources, the marine and coastal ecosystems of the world deal with pollution at levels that few fully realize. Major sources of pollution include debris, oil spills, polluted runoff, and sewage wastewater, and all of it is a result and byproduct of human activities. While there have been numerous international agreements and conventions that focus on the regulation of marine pollution, much further progress is still needed.

In their effort to create internationally known resorts, developers have entered into fragile coastal and marine habitats. Cruise ships, carrying ten of thousands of people every year, travel the waterways of the world dumping waste in the oceans. Nevertheless, the tourism industry has also contributed positively to the marine environment. Ecotourism, described as ecologically sustainable tourism, has revolutionized how many people travel and interact with local communities and the surrounding environment. In addition, there has been a growing effort on the part of the tourism industry to improve unsustainable practices and thereby have less adverse impacts on the environment.

IN DEPTH: Learn how to travel sustainably