An Assessment of Ecosystem Services and Biodiversity in Europe

ALASTAIR FITTER, THOMAS ELMQVIST, ROY HAINES-YOUNG, MARION POTSCHIN, ANDREA RINALDO, HEIKKI SETÄLÄ, SUSANNA STOLL-KLEEMANN, MARTIN ZOBEL AND JOHN MURLIS

ABSTRACT

Ecosystem services are the benefits humankind derives from the workings of the natural world. These include most obviously the supply of food, fuels and materials, but also more basic processes such as the formation of soils and the control and purification of water, and intangible ones such as amenity, recreation and aesthetics. Taken together, they are crucial to survival and the social and economic development of human societies. Though many are hidden, their workings are now a matter of clear scientific record. However, the integrity of the systems that deliver these benefits cannot be taken for granted, and the process of monitoring them and of ensuring that human activity does not place them at risk is an essential part of environmental governance, not solely at a global scale but also regionally and nationally.

In this chapter, we assess the importance of ecosystem services in a European context, highlighting those that have particular importance for Europe, and we set out what is known about the contribution biodiversity makes to each of them. We then consider pressures on European ecosystem services and the measures that might be taken to manage them.

One of the key insights from this work is that all ecosystems deliver a broad range of services, and that managing an ecosystem primarily to deliver one service will reduce its ability to provide others. A prominent current example of this is the use of land to produce biofuels. There is an urgent need to develop tools for the effective valuation of ecosystem services, to achieve sustainable management of the landscape to deliver multiple services.

1 Introduction

1.1 Biodiversity and Ecosystem Services: Why this Topic Matters Now

The past 50 years have seen an unprecedented human impact on ecosystems and on their biodiversity. Current rates of species extinction substantially exceed background extinction rates: International Union for Conservation of Nature (IUCN) estimates that 12% of bird species, 23% of mammals, 32% of amphibians and 25% of conifers are threatened with extinction. Human use of natural resources has grown substantially in this period: roughly half of useable terrestrial land is now devoted to grazing livestock or growing crops. That expansion has been at the expense of natural habitat, so that between a quarter and a half of all primary production is now diverted to human consumption. Other major threats to biodiversity include the introduction of non-indigenous species, pollution, climate change and over-harvesting. In marine ecosystems, over-exploitation of stocks has been the most severe cause of ecosystem degradation and local extinction.

These changes have considerable implications for human society. Living organisms, interacting with their environment in the complex relationships that characterise ecosystems, deliver important, and in some cases crucial and unsubstitutable, benefits to humankind. Most obviously, organisms provide goods in the form of food, fuel and materials for building, but they also deliver other, less apparent services. For example, insects, especially bees, play an important role in the pollination of plants, including staple food crops, and micro-organisms recycle or render harmless the waste produced by human society. Both the bees and the microbes operate within and rely on ecosystems for their survival.

These natural services are of enormous value to human society. Many of the services are irreplaceable: for example, we have no way of providing food for the human population except through the use of natural systems involving soil, soil organisms and crop plants, nor of providing drinking water, except through the operation of the water cycle, which depends critically on the activities of organisms. The maintenance of ecosystems, therefore, must be an essential part of the survival strategy for human societies.

Despite these benefits, investment in conservation does not match the scale of the benefits received from ecosystem services. It was noted by David Pearce that 'actual expenditures on international ecosystem conservation appear to be remarkably small and bear no relationship to the willingness to pay figures obtained in the various stated preference studies'. Pearce concluded 'despite all the rhetoric, the world does not care too much about biodiversity conservation'. This disconnection may arise in part because the links between biodiversity and ecosystem function (and consequently to ecosystem services) remain new areas of research: this chapter assesses the evidence for these links, focussing on ecosystem services that are of major concern for Europe.

The power of economic analysis in policy-making is such that argument about policy is typically constructed in a major part through the language of costs and benefits. There is an urgent need to address the chronic underinvestment in conservation of biodiversity and to ensure that future decisions do not lead to an unacceptable loss. This means that it is essential that the value of biodiversity in promoting the delivery of essential and valuable services is expressed strongly (in both economic and other terms) in those areas of decision-making where economic analysis is itself strongest.

1.2 The Current Assessment

The principal focus of assessment of ecosystem services to date has been at a global level. The Millennium Ecosystem Assessment (MA) continues to be a major influence on the development of a global regime for the protection of biodiversity through the Convention on Biological Diversity (CBD). At a national scale, UK National Ecosystem Assessment (NEA), which commenced in mid-2009 and will report in 2011, is expected to have a significant impact on the UK's environmental management strategy. There is also an urgent need to advance the development of regional measures for protecting biodiversity and ensuring the continual flow of ecosystem services. The assessment on which this chapter is based was commissioned by the Council of the European Academies Science Advisory Council (EASAC), an independent association of the science academies of the European Member States, as a contribution to the scientific debate on the future of European biodiversity and measures to protect it.

The assessment consists of four stages:

1. Prioritisation of ecosystem services within a European context using the MA framework;

2. Assessment of the relative significance of biodiversity for each of these services;

3. An evaluation of the role of biodiversity, based on current knowledge; and

4. Identification of specifically European concerns about the future of each ecosystem service.

The initial assessment was made by an expert Working Group. Following extensive review by a wide range of experts, comments and contributions from reviewers were assimilated and the output was subject to a review within the EASAC Member Academies. We believe, therefore, that this assessment is an accurate reflection of the range of views within Europe's scientific communities on ecosystem services and biodiversity in Europe.

2 Biodiversity and Ecosystem Services

2.1 Ecosystem Services

An ecosystem is the interacting system of living and non-living elements in a defined area. Ecosystems can exist at any spatial scale, although in most uses they are large-scale entities, such as a lake or a forest. The importance of the ecosystem is that it is the level in the ecological hierarchy (see Figure 1) at which key processes such as carbon, water and nutrient cycling and productivity are determined and can be measured: these are the processes that determine how the world functions and that underlie all the services identified by the MA.

The MA classification of ecosystem services contains four categories – supporting, regulating, provisioning and cultural – which explicitly address the benefits to human societies. The delivery of these services, however, represents the normal operation of the ecosystem, and reflects the natural processes that occur within every ecosystem. The services, therefore, which are a human construct, depend on these underlying processes, such as:

• Fixation of nitrogen gas from the air by bacteria into forms that are useable by plants, which underlies the nitrogen cycle;

• Decomposition of organic matter by microbes, which is the basis of all nutrient cycles, including importantly the carbon cycle; and

• Interactions between organisms, such as competition, predation and parasitism, which control the size of their populations, and underlie services such as pest control.

Because the processes depend on organisms and the organisms are linked by their interactions, the services themselves are also linked. For example, productivity can only be maintained if the cycling of nutrients continues, and all provisioning services depend intimately on the supporting services of production and water and nutrient cycling. Consequently all ecosystems deliver multiple services, although the number of species and the relative scale of the various services will vary greatly among ecosystems.

2.2 Relationships between Biodiversity and Ecosystem Services

Ecosystems vary greatly in biodiversity. Generally, productive natural ecosystems have the highest biodiversity but many highly productive ecosystems, and especially those under human management, have low biodiversity, showing that many other factors are at work. Among those factors are: rates of evolution, which are the underlying driver of biodiversity; rates of dispersal, both natural and assisted by humans, which are especially important when ecosystems are isolated from others by natural barriers; and the interactions between species, such as predation, competition and parasitism, which control the sizes of their populations and often their persistence in a community.

In ecosystems with many species, species can be grouped into sets that have similar ecological roles, called functional groups, for example, legumes which form a symbiosis with nitrogen-fixing bacteria in their roots and gain access to the pool of atmospheric nitrogen for their nutrition. Similarly, spiders that catch prey in webs and those that do so by hunting represent distinct functional groups of predators and play distinct roles in an ecosystem. Even where, in a biodiverse ecosystem, there are many species within a functional group, some will be rare and others common. Some species play especially important roles in the ecosystem, although these keystone species may not necessarily be common species. Losing an entire functional group from an ecosystem or the keystone species from within that group is likely to have more severe consequences for its functioning than losing one species from a large group, and such a loss is most likely in a species-poor system. Experimental evidence shows that both number of species and number of functional groups can play an important role in controlling ecosystem processes.

Ecosystems can change drastically when sets of key species are lost, or when new species invade. One of the great unsolved problems in ecology is to determine how important biological richness is for the operation of processes such as production and nutrient cycling. When there are more species in an ecosystem, and especially more types of species with distinct functional attributes, ecosystem processes, and the services they support, such as biomass production, pollination and seed dispersal are promoted, but the evidence is less clear as to what happens to an ecosystem as it progressively loses species. Because processes in ecosystems with very low biodiversity are in many cases slower or less active, it follows that loss of species will eventually cause degradation of processes. Although the shape of the relationship is not entirely clear (do services decline progressively or suddenly as biodiversity is lost?) there is evidence that it is highly non-linear. A slight decreasing trend in ecosystem functions as species diversity declines may be followed beyond a certain threshold with a collapse of function.

There are numerous well-documented examples that demonstrate that biodiversity plays a large role in the case of many services. Within the context of the Millennium Ecosystem Assessment framework, such examples would include:

• Supporting services: in a meta-analysis of 446 studies of the impact of biodiversity on primary production, 319 of which involved primary producer manipulations or measurements, there was 'clear evidence that biodiversity has positive effects on most ecosystem services', and specifically that there was a clear effect of biodiversity on productivity.

• Regulating services: in an experimental study of pollination in pumpkins it was the diversity of pollinator species, and not their abundance, that determined seed set.

• Provisioning services: where grassland is used for biofuel or other energy crop production, the lower financial return makes intensive production systems involving heavy use of pesticides and fertilisers uneconomic. Under these less intensive production systems, mixed swards of grasses are more productive than pure swards.

• Cultural services: evidence from the 2001 foot and mouth disease epidemic in the UK demonstrated that the economic value of biodiversity-related tourism greatly exceeds that of agriculture in the uplands of the UK.

2.3 Land Use and Multiple Services

Land use has a major impact on both ecosystem services and biodiversity, especially when altered by human activity to deliver some particular service, such as food production in agro-ecosystems. However, all ecosystems deliver multiple services, and management to maximise one particular service risks reducing others. For example, forests regulate water flow and quality and store nutrients in soil, among many other functions; clear-felling a forest to obtain the ecosystem service of timber products results in the temporary failure of the system to retain nutrients, as shown by the classic Hubbard Brook experiments in New England, USA. Similarly, arable land managed to maximise yield of food crops stores less carbon in the soil, with negative effects on the service of climate regulation.

Human impact on ecosystems is most extreme in intensive agriculture and in urban landscapes. Urban ecosystems typically contribute minimal levels of provisioning services. Urban landscapes are characteristically heterogeneous, including in relation to biodiversity. Street trees and urban vegetation may generate services of high value for human well-being related to environmental quality such as air cleaning, noise reduction and recreation, or to human health (asthma rates among children aged four and five in New York City were directly proportional to the density of trees). Because of the density of human population, many urban ecosystem services are generated on a very small scale, by patches of vegetation and even individual trees.

Land (and where appropriate water) management always, even if only implicitly, aims to achieve benefits of one or more ecosystem services, but because these services are not independent of one another, there are trade-offs between the services.

• Temporal trade-offs: there may be benefits now with costs incurred later (or more rarely vice versa). Land used for food production may store progressively declining stocks of organic matter, with long-term consequences both for nutrient cycling, and hence future fertility, and carbon sequestration.