Atmospheric concentration of CO2 is steadily rising, and oceans directly assimilate CO2. As ocean concentration of CO2 increases, the oceans automatically become more acidic. This, in turn, may have severe impacts on coral reefs and other biocalcifying organisms. There is little debate on the effect as this is a straight-forward chemical process, but the implications for marine life, that may be severe due to many very pH-sensitive relationships...

About shelfwater

All across the planet, the number and severity of outbreaks and infestations of invasive species (i.e. species purposefully or accidentally introduced in non-native environments) is growing, and invasions of marine habitats are now occurring at an alarming rate. Exotic and invasive species have been identified by scientists and policymakers as a major threat to marine ecosystems, with dramatic effects on biodiversity, biological productivity, hab...

Each of the big five stressors (not in order of magnitude), 1) Climate change; 2) Pollution (mainly coastal), 3) Fragmentation and habitat loss (from e.g. dredging/trawling, use of explosives in fishing on coral reefs etc.), 4) Invasive species infestations, and 5) Over-harvest from fisheries may individually or combined result in severe impacts on the biological production of the worlds oceans and the services they provide to billions of people ...

The impacts of coral reefs from rising sea temperatures. When coral reefs become heat-exposed they die, leaving the white dead coral, also known as bleaching. With even moderate pollution, the coral are easily overgrown with algae, or broken down by wave activity or storms, leaving only “coral rubble” on the ocean bed.

The locations of major problem areas for invasive species infestations or occurrence of exotic species in the marine environment. The impacted areas are concurrent with the areas subjected to the worst pollution, the most intensive fisheries and bottom trawling, and major shipping routes. The areas in the figure have been highlighted based on an overview of literature, and the delineation of the areas are approximate.

About scenarios

Tropical cyclones, or hurricanes or typhoons, are storm weather systems, characterised by a low pressure centre, thunderstorms and high windspeeds. As the name testifies, these occur in the areas between the tropics, in the tropical areas. Cyclones can, after they have formed in the oceans, move in over populated areas, creating much damage and even natural disasters.

The world's marine fisheries have stagnated or slightly declined in the last decade, offset only by increases in aquaculture production. A major reason why the decline has not become more evident is likely because of advances in fishing efficiency, shift to previously discarded or avoided fish, and the fact that the fishing fleet is increasingly fishing in deeper waters

Water has long been associated with conflicts between neighbouring countries. This graphic shows how water from the Tigris and Euphrates rivers is used in Iraq, and that neighbouring Syria and Turkey influence the flow of this water. The graphic shows the locations of main dams, swamps and horticulture in the region. It also shows five of the major ways in which land is used in the region: forest and grazing land; rain-fed agriculture (grains, ve...

The Global International Waters Assessment (GIWA) is an example of a comprehensive strategic assessment designed to identify priorities for remedial and mitigatory actions in international waters. This graphic shows GIWA case studies for the Black Sea, the Amazon, the Great Barrier Reef and the Agulhas Current. Each case study includes an introduction and maps of the region and a discussion of the issues of concern for that region, such as freshw...

River flow is cyclical in nature, with alternating cycles of wet and dry years. This graphic uses bar graphs to show the average annual volumes of river runoff in cubic kilometres for each continent from 1921 to 1985. Over the time period the discharge there has been no obvious trends, but a certain degree of fluctation, the level dependent on the area of the basins and the precipitation over the area. The sizes of the bars in this graph reflect ...

Global International Waters Assessment's (GIWA) assessment tools for monitoring the world's water resources, incorporating five major environmental concerns and application of the DPSIR framework (driving forces-pressure-state-impact-response), are now beginning to yield results of practical use for management decisions. This graphic explains the GIWA Assessment Methodology and GIWA's five main environmental concerns, which are: freshwater shorta...

Coastal areas with high population densities are those with the most shoreline degradation or alteration. Densely populated areas close to seas are also the most attractive for a lot of economic activity. The graphic shows the proportion of the population that lives within 100 km of the coast, for each of the world's nations and where there are coastal zones with high degree of human alteration (compared to 'natural' landcover). In addition, the ...

Besides the well-known economic value of fisheries, there are several other activities generating significant revenues in coastal and marine areas. This graphic discusses the economic benefits of coastal tourism, trade and shipping, offshore oil and gas, and fisheries. It also illustrates the estimated mean value of marine biomes such as estuaries and coastal reefs.

The global fisheries catch has levelled off, reflecting a growing decline in most major fishing areas. This graphic shows the amount of global aquaculture production and of global capture fishery catches in millions of tonnes per year for 1950 to 1999. The graphic also shows the amounts of global aquaculture production in marine water, freshwater and brackish water, in millions of tonnes, for 1998.

Asia exhibits the largest runoff volumes and, therefore, the highest levels of sediment discharge. This graphic shows the amounts of suspended sediments discharged, in millions of tonnes per year, in the major regions of the world. The levels of suspended sediments are increased by soil erosion and land degradation, and may affect aquatic ecosystems negatively.

Glaciers and icecaps contain approximately 70% of the world's freshwater, but groundwater is by far the most abundant and readily available source of freshwater. This graphic illustrates the quantity (in cubic kilometres) and distribution of the world's freshwater resources in glaciers and permanent ice caps, in groundwater, and in wetlands, large lakes, reservoirs and rivers. Further information is given in the accompanying text.

Freshwater use is partly based on several socio-economic development factors, including population, physiography, and climatic characteristics. This graphic illustrates freshwater use, in cubic kilometres per year, from 1900 to 2000 for the world's major regions, and projects freshwater use for 2000 to 2025. It also shows how much water was withdrawn and consumed, in cubic kilometres per year, by each continent at the end of the 1990's. Finally, ...

The demise of the Aral Sea was caused primarily by the diversion of the inflowing Amu Dar'ya and Syr Dar'ya rivers to provide irrigation water for local croplands. This graphic shows the disappearance of the Aral Sea from 1957 to 2000 and three possible scenarios showing the relationship between future demand (and thus water abstraction) and future available runoff in cubic kilometres per year. The scenarios cover the time period from 2000 to 202...