Ecosystem services provided by the Baltic Sea ... - Naturvårdsverket

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SWEDISH ENVIRONMENTAL PROTECTION AGENCY Report 5873 • Ecosystem services provided by the Baltic Sea and Skagerrak Economic Marine Information Supporting ecosystem services S4: Maintenance of biodiversity Definition Biological diversity, or biodiversity for short, refers to the variety of life forms at all levels of organization from the molecular to the landscape level. A variety of species performing a plethora of functions are essential for most ecosystem services. Of direct benefit to society is the supply of various species for consumption. Of indirect benefit is the maintenance of resilience. Out of convenience, biodiversity typically refers to a function of the number of species and the number of individuals of each species in a given area. Functional diversity is an important aspect of biodiversity which refers to variation among ecological functional processes (often related to feeding patterns or interactions among species) within an ecosystem. It should be kept in mind that genes, species, ecological functions and ecosystems are not equal - some are indeed more important than others. Three important paradigms of biodiversity 1) More diverse ecosystems are generally more productive and more stable (46) 2) Biodiversity contributes largely to goods and services of the ecosystem (47) 3) Biodiversity is diminishing on the high rate due to man’s activity (48) Related processes and services The benefits of biodiversity to other ecosystem services are numerous. Biodiversity typically enables an ecosystem to perform a variety of functions, thus providing various ecosystem services, while buffering against natural and human-induced disturbance (chapter S6). The potential of diversity (particularly functional and genetic) to maintain resilience and support resource extraction may become increasingly critical in the current light of global environmental change. For example, in the event of a disturbance, functional diversity – or the existence of more than one species carrying out the same function in the ecosystem (like grazing, filtering water and bioeroding) is crucial in order to maintain ecosystem function. Similarly, the existence of genetically distinct individuals and populations promotes resistance to various environmental stressors, like drops in salinity, pH and increased temperatures (49). Also in defence against invasive alien species, diversity appears to be an important factor (50). Maintenance of biodiversity is dependent on all supporting as well as most regulating services. It requires availability of habitat, primary production and is related to food web dynamics. It further calls for efficient biological regulation, mitigation of 49
SWEDISH ENVIRONMENTAL PROTECTION AGENCY Report 5873 • Ecosystem services provided by the Baltic Sea and Skagerrak Economic Marine Information unregulated eutrophication and pollution control. A recent model confirms the interactions between habitat availability, biodiversity and the provision of ecosystem services (51). The model demonstrates how the decline in the provisioning of ecosystem services due to biodiversity loss is initially slow, but then accelerates, as species from higher trophic levels are lost at faster rates. Empirical studies of ecosystem collapse support these results Status, threats and consequences Status Moderate Sustainability of use - Level of threat High Expected consequences Unknown The rapid loss of biodiversity is alarming, and with current levels of anthropogenic impact, the situation may become increasingly critical for a number of marine species. This is likely to have consequences for ecosystem function. Yet, due lack of knowledge about many marine species, particularly those that are rare or threatened, it is hard to determine the extent of these consequences. Global marine biodiversity Diversity at higher taxonomic levels (phyla and classes) is much greater in the sea than on land or in freshwater. Of the 82 or so eukaryote phyla currently recognised, around 60 have marine representatives somewhere in the world. Some 23 eukaryote phyla, of which 18 are animal phyla, are confined to marine environments. Most of these are relatively obscure and comprise few species. One major exception is the Echinodermata (including starfish, sea urchins and sea cucumbers), of which some 6000 species are known. Worldwide, only 2 % of all marine species are estimated to live in the water column, whereas the rest are associated to the sea floor. Highest diversity is found on hard substrates while soft bottoms harbour a lower number of species (52). Marine biodiversity remains elusive Most scientific knowledge regarding biodiversity is based on terrestrial ecosystems. Increased awareness of particularities in the marine ecosystem is however increasing. For example, the risk of cascading effects is believed to be greater in the marine environment than on land, making loss of biodiversity more severe in the marine environment (chapter S3). A typical scenario in the marine environment is that species become ecologically extinct, in the sense that they do not disappear entirely, yet they lose their importance in the local ecosystem. A single drop of sea water can contain as much as one million bacteria, 100 unicellular flagellates, ten phytoplankton, one ciliate and 0.001 zooplankton. Because so much of the ocean is only accessible with expensive technology and remote in- 50
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