Coastal ecosystems, found along continental margins, are regions of remarkable biological productivity and high accessibility. This has made them centers of human activity for millennia. Coastal ecosystems provide a wide array of goods and services: they host the world’s primary ports of commerce; they are the primary producers of fish, shellfish, and seaweed for both human and animal consumption; and they are also a considerable source of fertilizer, pharmaceuticals, cosmetics, household products, and construction materials.

Encompassing a broad range of habitat types and harboring a wealth of species and genetic diversity, coastal ecosystems store and cycle nutrients, filter pollutants from inland freshwater systems, and help to protect shorelines from erosion and storms. On the other side of shorelines, oceans play a vital role in regulating global hydrology and climate and they are a major carbon sink and oxygen source because of the high productivity of phytoplankton. The beauty of coastal ecosystems makes them a magnet for the world’s population. People gravitate to coastal regions to live as well as for leisure, recreational activities, and tourism.

For purposes of this analysis, the coastal zone has been defined to include the intertidal and subtidal areas on and above the continental shelf (to a depth of 200 meters) and immediately adjacent lands. This definition therefore includes areas that are routinely inundated by saltwater. Because the definition of coastal ecosystems is based on their physical characteristics (their proximity to the coast) rather than a distinct set of biological features, they encompass a much more diverse array of habitats than do the other ecosystems in the Pilot Analysis of Global Ecosystems (PAGE), such as grasslands or forests. Coral reefs, mangroves, tidal wetlands, seagrass beds, barrier islands, estuaries, peat swamps, and a variety of other habitats each provides its own distinct bundle of goods and services and faces somewhat different pressures.

Scope of analysis

This study analyzes quantitative and qualitative information and develops selected indicators on the condition of the world’s coastal zone, where condition is defined as the current and future capacity of coastal ecosystems to provide the full range of goods and services needed or valued by humans.

In addition to assessing the condition of the different coastal habitats, with the exception of continental slope and deep-sea habitats, the PAGE analysis also includes marine fisheries. The bulk of the world’s marine fish harvest—as much as 95 percent, by some estimates—is caught or reared in coastal waters (Sherman 1993:3). Only a small percentage comes from the open ocean. This study relied on global and regional data sets provided by many organizations, including the United Nations Environment Programme-World Conservation Monitoring Centre (UNEP-WCMC), the Food and Agriculture Organization of the United Nations (FAO), the World Wildlife Fund-US (WWF), IUCN- The World Conservation Union, and others. These global and regional data sets generally focus on a single issue or distinct habitat type, and rarely cover the entire coastal ecosystem. The PAGE analysis also benefited from a variety of national assessments and reviews that provide a wealth of information for certain countries, particularly the United States, Australia, and parts of Europe. These reviews attempt to integrate and summarize the best available information to develop a comprehensive picture of the status of coastal ecosystems. Most of these efforts, however, remain hampered by the limited availability and inconsistencies of the data, and therefore rely heavily upon expert opinion. In addition to these global, regional and national data sets, the PAGE analysis also used case studies from around the world to illustrate important issues, concepts, and trends in the coastal zone.

Because of the lack of global data on coastal habitats, a large part of the efforts in this analysis went into identifying data and information gaps, as well as developing useful, but often proxy, indicators to assess the condition of goods and services derived from coastal ecosystems. Throughout the study the emphasis was placed on quantitative and geographically referenced information.

As mentioned earlier, the coastal zone provides goods and services of immeasurable value to human society. The goods from marine and coastal habitats include food for humans and animals (including fish, shellfish, krill, and seaweed); salt; minerals and oil resources; construction materials (sand, rock, coral, lime, and wood); and biodiversity, including the genetic stock that has potential for various biotechnology and medicinal applications. The services provided by coastal ecosystems are less readily quantified in absolute terms, but are also invaluable to human society and to life on earth. These include shoreline protection (buffering the coastline, protecting it from storms and erosion from wind and waves), storing and cycling nutrients, sustaining biodiversity, maintaining water quality (through filtering and degrading pollutants), and serving as areas for recreation and tourism.

This analysis only considers a subset of goods and services derived from coastal ecosystems. The five categories considered are:

• Shoreline stabilization;
• Water quality;
• Biodiversity;
• Food production – marine fisheries; and
• Tourism and recreation.

Other more limited services such as marine transport, including port facilities and channel dredging, are not considered even though marine transport has shaped the development of human history and remains of critical importance today. Likewise, extractive activities, such as the mining of minerals or extraction of oil and construction materials, are not covered.

This study also excludes discussion of the global climate and hydrologic functions of the oceans. Examining these services would be more appropriate in an assessment of the entire marine environment. Activities in the coastal zone only play a small role in the overall volume, carbon storage, and heat storage capacity of oceans. As such, the topic of oceans as climate regulators is beyond the scope of this report.

Key Findings and Information Issues

The following tables summarize the study’s key findings regarding the condition of coastal ecosystems and marine fisheries, as well as the quality and availability of the data.

Conclusions

Along with direct loss of area, a variety of other factors are significantly altering coastal ecosystems around the world. Some of the major pressures are population growth, pollution, overharvesting and destructive fishing practices, and the looming threat of climate change.

Globally, the number of people living within 100 km of the coast increased from roughly 2 billion in 1990 to 2.2 billion in 1995—39 percent of the world’s population. However, the number of people whose activities affect coastal ecosystems is much larger than the actual coastal population because rivers deliver pollutants from inland watersheds and populations to estuaries and surrounding coastal waters. As coastal and inland populations continue to grow, their impacts—in terms of pollutant loads and the development and conversion of coastal habitats—can be expected to grow as well.

An increasing number of pollutants affect the world’s coasts and oceans. Most pollution of coastal waters comes from the land, but atmospheric sources and marine-based sources such as oil leaks and spills from vessels also play a role. Nutrient pollution, especially nitrates and phosphates, has increased dramatically this century. Greater use of fertilizers, growth in quantities of domestic and industrial sewage, and increased aquaculture, which releases considerable amounts of waste directly into the water, are all contributing factors (GESAMP 1990:96).

In terms of food production, forty-five years of increasing fishing pressure have left many major fish stocks depleted or in decline. The scale of the global fishing enterprise has grown rapidly and exploitation of fish stocks has followed a predictable pattern, progressing from region to region across the world’s oceans. As each area in turn reaches its maximum production level, it then begins to decline (Grainger and Garcia 1996:8, 42–44). Overexploitation of fish, shellfish, seaweeds, and other marine organisms not only diminishes production of the harvested species but can profoundly alter species composition and the biological structure of coastal ecosystems.

Global climate change may compound other pressures on coastal ecosystems through the additional effects of warmer ocean temperatures, altered ocean circulation patterns, changing storm frequency, and rising sea levels. Changing concentrations of CO2 in ocean waters may also affect marine productivity or even change the rate of coral calcification (Kleypas et al. 1999). Rising sea level, associated with climate change, is likely to affect virtually all of the world’s coasts. During the past century, sea level has risen at a rate of 1.0–2.5 mm per year (IPCC 1996:296). Rising sea levels will also increase the impact of storm surges. This, in turn, could accelerate erosion and associated habitat loss, increase salinity in estuaries and freshwater aquifers, alter tidal ranges, change sediment and nutrient transport, and increase coastal flooding.

Because of the current pressures on coastal ecosystems, and the immense value of the goods and services derived from them, there is an increasing need to evaluate tradeoffs between different activities that may be proposed for a particular coastal area. However, to integrate this evaluation into the decisionmaking process, better information on the location, extent, and change in coastal habitats is urgently needed. Information regarding the interaction between ocean, land, and atmosphere is also a key to understanding the functions of the coastal zone but so far most of the information is anecdotal or fragmentary. One factor contributing to this lack of information is the partitioning of disciplines into separate entities. Terrestrial ecology, wetland ecology, and marine ecology are, for example, distinct fields among the biological sciences. The separation between these and the physical, chemical, and social sciences is even greater, making it difficult to conduct a more integrated analysis. The problems affecting the coastal zone are cross-sectoral and complex. Collaboration among climatologists, ecologists, ocean chemists, toxicologists, soil scientists, statisticians, coastal engineers, economists, and practitioners of monitoring and information technology will be needed to develop the information base and linkages necessary to fully assess the condition of the world’s coastal environments.

Recommendations for the Millennium Ecosystem Assessment include the following:

• There is an urgent need to fully utilize existing information on location and extent of coastal habitats. Standardized classification schemes characterizing the world’s coasts need to be developed. Amalgamating and harmonizing existing maps and chart series into global data sets based on such classification schemes, combined with the use of high-resolution remote sensing imagery, could more directly assess gaps in knowledge on the location and extent of coastal habitats. Particular efforts need to be directed toward submerged habitats.
• Further descriptive information about the distribution and status of marine and coastal biodiversity is a priority. Basic inventory of coastal and marine species by habitat type is fundamental to subsequent research, management, and conservation. Work needs to include basic taxonomy and species inventory, but also analysis of community structure, ecosystem function, and habitat distribution.
• Identifying and describing areas of high conservation importance at species and ecosystem levels would help improve the effectiveness of conservation activities. Further research into the patterns of interlinkage and energy flow between marine ecosystems is also critical if such high priority areas are to maintain their ecological integrity.
• Compilation of historic or baseline data against which we may measure the condition of ecosystems is a prerequisite for any assessment of current status. Localized baseline data and the identification of thresholds are particularly important for water quality. In order for the condition indicators to be useful as early warning systems, it is important to distinguish between human caused anomalies and natural fluctuations in the system.
• Causal relationships in biological, chemical, and physical systems are also poorly understood, and in the coastal realm are particularly complex and varied. Our predictive capabilities are limited when we attempt to examine how certain threats affect an environment, such as the introduction of nonnative species. Understanding links between pressure and condition would improve our assessment of future trends and human activities that may have profound implications for coastal habitats and biodiversity.
• In many cases, combining the use of low, medium, and high-resolution satellite imagery will be vital to calibrating data and refining observations for conditions in nearshore and surface waters. Satellite data will be useful for habitat mapping, estimating turbidity and organic pollutant discharge, identifying sediment plumes, monitoring the occurrence and extent of algal blooms, mapping the occurrence and extent of oil spills, and monitoring thermal pollution and sea surface temperature anomalies. At the same time, other more direct methods need to be developed to map and monitor the status of the continental shelf, which lies below the shallow layers visible from satellites.
• More integration and collaboration among the various agencies working in the coastal zone, particularly with the different monitoring initiatives, such as the Global Ocean Observing System (GOOS) should be encouraged (GOOS Project Office 1998 and 1999; Summerhayes, personal communication, 1999). Such organizations include the United Nations Environment Programme (UNEP), the Intergovernmental Oceanographic Commission (IOC), the United Nations Educational, Scientific, and Cultural Organization (UNESCO), the United Nations Development Programme (UNDP), the Food and Agriculture Organization of the United Nations (FAO), the International Geosphere-Biosphere Programme (IGBP), nongovernmental organizations, and academic centers.
• There is a need to better understand, evaluate and monitor the goods and services provided by coastal and marine ecosystems.
• Governments and nongovernmental organizations are encouraged to develop techniques for engaging policymakers and civil society so they can evaluate tradeoffs and make decisions with greater understanding and awareness of the consequences.