From the earliest times, the areas of important global economic activity has been concentrated in the coastal zone (Sachs et. al 2000), with settlements often growing on the continental margins to take advantage of overseas trade and easy access to the resources of the rural hinterlands.
As a result, the coastal zone has attracted large and growing populations, with much of their growth attributable to migration rather than natural increase (Henrichsen, 1998).
Today, 10% of the world’s population lives at less than 10 m above sea level (even though this area only accounts for 2.2% of the world’s land area), and coastal zones have higher population densities than any other ecologically delineated zone in the world.
Coastal and marine environments are very important for human health and well- being, and they are also quite vulnerable to anthropogenic impacts (McGranahan, 2007).
Not surprisingly, over half of the world’s coastlines are at significant risk from development-related activities (Faye et. al., 2004), and the potential (and realized) environmental damage is substantial.
Population growth is often named as the driver of coastal and marine environmental challenges, whereas proximate causes can be traced to specific practices (Bryant et al 1998).
Population growth can lead to many other coastal and marine environmental disturbances e.g. tropical mangroves are being cleared for fish and shrimp aquaculture farms, which undermine coastal protection and decreases natural habitat that many fish species use for reproduction.
Expanding coastal cities undermine natural protection from storms and hurricanes and also increase pollution and runoff. Additionally, untreated sewage and agricultural runoff continue to be a worldwide problem.
Although listed as a driver, like other issues, the impact of population size and growth depends on many other factors such as the sensitivity of coastal systems to stress, local habits, and markets.
For example, demand for shrimp is the ultimate driver of mangrove loss, and sewage treatment systems and no-till agriculture could significantly reduce nutrient loading in coastal areas (Faye et al 2004).
The relationship between human activities and environmental impacts are hard to assess and regulate in coastal and marine environments because the environmental resources are almost always governed by Common Property Resource (CPR) management systems typical of developing countries, whereas terrestrial environments are generally managed by the government or private sectors.
CPR management systems may be especially vulnerable to disruption caused by in-migration, urbanization and increase in population. However, the social and economic context largely determine whether in- migration and population pressure disrupt the CPR system and thus cause environmental degradation (Curran 2002).
Studies in developing countries on population increase and the marine environment have focused on a mediating approach, such as how technology, local knowledge, social institutions of kinship or marriage and markets mediate the role of population in resource extraction and consequent environmental degradation or enhancement.
In another study in the Solomon Islands contests the notion that sea tenure regimes are weakened by in-migration and population growth. Potentially negative impacts of population pressure on the environment are diminished significantly with greater reciprocal consequences among close kin or neighbours (Aswani 2002).
Human impacts on coastal and marine environments are not a simple function of population size or density, other factors such as technology, knowledge, social activities, common property systems, migration, and the economic and ecological context in which these interactions take place all play an important role in population and environment relationships, especially in developing countries.
Nonetheless, coastal and marine environments continue to be among the most threatened ecosystems in the world, owing in part to the sheer scale of detrimental human activities associated with urbanization along the coasts, continued population growth, and a growing number of tourists in search of coastal amenities and beauty (Aswani 2002).