Pollution and poor land use practices within these watersheds affect downstream marine habitats because sediments and pollutants are ultimately washed into coastal waters. Pressures on marine ecosystems include coastal population density and continued population growth, which are accompanied by increased consumer demand for marine products, increased waste disposal, rapid alteration of coastal habitats, uncontrolled industrial pollution, inadequate institutional structures for managing marine resources, lack of property rights and management regimes within international waters, and lack of understanding and awareness of marine ecosystem processes and the effects of human actions on marine biodiversity. The Black Sea, for example, is dying under the weight of pollution and overfishing. Land-based pollution in the form of industrial wastes, sewage, and runoff of pesticides and fertilizers, combined with oil and other wastes from ship traffic, have contaminated the entire basin. Habitat Loss Habitat conversion and degradation are generally thought to be the most significant threats to terrestrial life.
Coastal development contributes to habitat loss in a number of ways.
These include conversion of mangroves and other wetlands as a result of urbanization and agricultural expansion, the building of shoreline stabilization structures such as breakwaters, mining, oil drilling, and dredging and filling. Damming of rivers and water diversion projects lead to changes in downstream estuarine and marine communities, because interruption of freshwater flow changes the physical environment of such areas and the amount of nutrients that they receive. Intense exploitation of marine resources can indirectly lead to habitat loss. Fishing with dynamite and harvesting of corals are major threats to coral reef areas. Much of the global fishing effort is targeted at a few species, located primarily near the top of the food chain.