B I O D I V E R S I T Y, E C O S Y S T E M S E R V I C E S , H U M A N I T Y ’ S F O O T P R I N T The Living Planet Index shows that wild species and natural ecosystems are under pressure across all biomes and regions of the world. The direct, anthropogenic threats to biodiversity are often grouped under five headings: ■ habitat loss, fragmentation or change, especially due to agriculture ■ overexploitation of species, especially due to fishing and hunting ■ pollution ■ the spread of invasive species or genes ■ climate change. All five of these threats stem ultimately from human demands on the biosphere – the production and consumption of natural resources for food and drink, energy or materials, and the disposal of associated waste products – or the displacement of natural ecosystems by towns, cities and infrastructure (see Figure 4). Further, the massive flows of goods and people around the world have become a vector for the spread of alien species and diseases. Natural habitat is lost, altered or fragmented through its conversion for cultivation, grazing, aquaculture, and industrial or urban use. River systems are dammed and altered for irrigation, hydropower or flow regulation. Even marine ecosystems, particularly the seabed, are physically degraded by trawling, construction and extractive industries. Overexploitation of wild species populations is the result of harvesting or killing animals or plants for food, materials or medicine, at a rate above the reproductive 4 LIVING PLANET REPORT 2008
capacity of the population. It has been the dominant threat to marine biodiversity, and overfishing has devastated many commercial fish stocks. However, overexploitation is also a serious threat to many terrestrial species, particularly tropical forest mammals hunted for meat. Overharvesting of timber and fuelwood has also led to loss of forests and their associated plant and animal populations. Invasive species, introduced either deliberately or inadvertently to one part of the world from another, and which become competitors, predators or parasites of indigenous species, are responsible for declines in many native species populations. This is especially important on islands and in freshwater ecosystems, where they are thought to be the main threat to endemic species. Pollution is another important cause of biodiversity loss, particularly in aquatic ecosystems. Excess nutrient loading as a result of the increasing use of nitrogen and phosphorous fertilizers in agriculture causes eutrophication and oxygen depletion. Toxic chemical pollution often arises from pesticide use in farming or aquaculture, from industry and from mining wastes. The increasing carbon dioxide concentration in the atmosphere is causing acidification of the oceans, which is likely to have widespread effects, particularly on shell- and reefbuilding organisms. Potentially the greatest threat to biodiversity over the coming decades is climate change. Early impacts have been felt in polar and montane as well as coastal and marine ecosystems, such as coral reefs. Future
impacts are difficult to predict at local scales, but any ecosystem may be susceptible to changing temperature or weather patterns. Clearly, all of these threats or pressures are the effect of more distant, indirect drivers. These drivers of biodiversity loss stem from the human demands for food, water, energy and materials. They can be considered in terms of the production and consumption of agricultural crops, meat and dairy products, fish and seafood, timber and paper, water, energy, transport and land for towns, cities and infrastructure. As the world population and economy grow, so do the pressures on biodiversity. As technology and resource efficiency improve, so the pressure could be alleviated. The Ecological Footprint is an aggregate measure of the demands that resource consumption places on ecosystems and species. Understanding the interactions between biodiversity, the drivers of biodiversity loss and humanity’s footprint is fundamental to slowing, halting and reversing the ongoing declines in natural ecosystems and populations of wild species. ECOSYSTEM SERVICES Humanity depends on healthy ecosystems: they support or improve our quality of life, and without them, the Earth would be uninhabitable. The Millennium Ecosystem Assessment (MA) describes four categories of ecosystem services, starting with the most fundamental: ■ supporting services such as nutrient cycling, soil formation and primary production ■ provisioning services such as the
production of food, freshwater, materials or fuel ■ regulating services including climate and flood regulation, water purification, pollination and pest control ■ cultural (including aesthetic, spiritual, educational and recreational) services. Each of these services derives ultimately from living organisms. However, it is not biodiversity per se that underpins ecosystem services, but the abundance of particular species that are critical in maintaining habitat stability and providing those services. Decline in a critical species at a local scale will have an adverse impact on ecosystem services, even if that species is not threatened globally. The MA reported that biodiversity loss contributes to food and energy insecurity, increased vulnerability to natural disasters such as floods or tropical storms, poorer health, reduced availability and quality of water, and the erosion of cultural heritage. Most supporting, regulating and cultural ecosystem services are not bought and sold commercially, so have no market value. Their decline sends no warning signal to the local or global economy. Markets lead to decisions about resource use that maximize benefits to individual producers and consumers, but often undermine the biodiversity and ecosystem services on which the production and consumption ultimately depend. The value of biodiversity to human well-being, while not readily quantifiable in monetary terms, could be the difference between a planet that can support its human population and one which cannot.