Daily (1997) defines ecosystems as a set of organisms living in an area, their physical environment, and the interactions between them. Ecosystem services are the conditions, processes and species that sustain life on this planet. Tilman (1997) argues that
biodiversity is thought to influence the supply of ecosystem goods and services.
Biodiversity is described as the variety of life at all levels of organisation, from genetic variation within and among species, to the level of variation within and among
ecosystems, and biomes.
Human activities are changing many ecosystems, some of these activities have resulted in benefits to humans in terms of food security and economic development, but these changes are now threatening ecosystem goods and services, and economic and social options, for current and future generations. The 2005 Millennium Ecosystem
Assessment reported that 60% of ecosystem services surveyed are being degraded or used unsustainably (Srinivasen et al., 2008). Ecosystems respond differently to
disturbance, and ecosystem stability may depend on biodiversity. Some ecosystems are not greatly impacted whereas others can be susceptible to disturbances, which may lead to a loss of productivity, and functioning of these ecosystems. The harvesting of species from ecosystems, such as fish, may be carried out on a sustainable basis (maintaining ecosystem function and biodiversity), or adverse practices might lead progressively to lower ecosystem productivity and biodiversity. The degradation of ecosystems pose a threat to maintaining ecosystem goods and services, so maintaining biodiversity and ecosystem sustainability is considered important, for both human and environmental well being (Tilman, 1997 pp. 93-109).
As Kaiser et al. (2005 p. 20) explain there are three main aspects of biodiversity ecological (biomes, ecosystems, habitats); organismal (kingdoms, phyla, species); and genetic (populations, individuals and genes). Diversity also occurs at a number of different levels – genetic, species, phyletic, functional, community, ecosystem and habitat, but all are important to marine biodiversity. There are also different spatial and temporal patterns of diversity (Gray, 1997). Conservation of biological diversity has been a major focus of recent international forums. As it is recognised that if biodiversity concerns are not taken into account, and the products and services provided by
biodiversity are not harvested on a sustainable basis, future options may become limited. In 2002 parties to the Convention on Biological Diversity (CBD) committed to actions to achieve by 2010 a significant reduction of the current rate of biodiversity loss at the global, regional and national levels. In 2004, the Biodiversity Liaison Group was created under five of the key global biodiversity related conventions (UN Convention on Biological Diversity, Convention on International Trade in Endangered Species, Convention on the Conservation of Migratory Species of Wild Animals, Ramsar and the World Heritage Convention) to help facilitate a more co-ordinated approach to policy development and implementation (Kaiser et al., 2005 p. 491; United Nations
Environment Programme (UNEP), 2007 pp. 160-189).
Although the understanding of the importance of biodiversity has developed over the past twenty years, biodiversity decline and loss has continued. Some biodiversity losses such as erosion of genetic variability in a population are often slow or gradual, and may
not be recognised until too late. Biodiversity loss continues because the values of biodiversity are insufficiently recognised by political and market systems. An added complexity is that the global nature of many biodiversity values, result in the loss being felt beyond national boundaries. While technological alternatives to some services provided by biodiversity are available, these are more costly when compared to those benefits derived from functioning ecosystems (United Nations Environment Programme (UNEP), 2007 pp. 160-189). The goods and services flowing from ecosystems are often undervalued by society, and their value has primarily become a focus of attention due to their disruption and loss, and a growing awareness of the limits and cost of
technological substitution (Daily, 1997 pp. 2-7).
Charles (2001 p. 32) describes natural capital in terms of ecosystem goods and services, which are critical to the functioning of the planet, and that fish stocks are only one part of the natural capital in the marine environment. Because ecosystem services are not captured in markets, their full value, are often not considered fully in the decision- making process. In 1997 Costanza et al. (1997) estimated that ecosystems provided at least US$33 trillion dollars worth of services annually, and most of this value was outside the market system. About 63% (US$20.9 trillion) of the estimated value was contributed by the marine system, with most contributed by coastal systems (US$4.7 trillion).
Costanza et al. (1997) acknowledge that these estimates have limitations as it is based on a static snapshot; it does, however, serve to highlight a number of important factors. In many respects the value of ecosystem services to the economy is infinite, and the interdependent nature of ecosystem functions and services are critical for human welfare. An important question is how changes in the quantity or quality of different types of natural capital and ecosystem services, may impact human welfare. The issue of valuation is linked to choices and decisions made by society about ecosystems. Costanza et al. (1997) suggest if ecosystems services were fully accounted for in the global market system, the global price system, and Gross National Product (GNP) would be different, as would the appraisal of the costs and benefits of particular human activities.