Extent To Which Biodiversity Underpins Ecosystem Services

Effects on services and processes as a whole

Increased biodiversity has notable positive effects on many ecosystem services that are useful to humans, which include climate regulation, seed dispersal, pollination, and pest and disease control. It also affects ecosystem processes such as soil formation, biomass production by plants and nutrient and water cycling (Díaz et. al., 2006). It also has effects on cultural services such as aesthetic enjoyment, education, recreation and spiritual fulfillment, although these are less studied and therefore more poorly understood (MA, 2005). Loss of biodiversity is likely to mean that the ability of ecosystems to provide these services is compromised (Balvanera et. al., 2006).

Research suggests that the function and structure of entire ecosystems can be drastically altered by the loss of certain species and a reduction in biodiversity has a non-linear impact on singular ecosystem processes. This means that the more biodiversity is lost, the faster the changes in processes happen. Also, the effect that biodiversity has on ecosystem services may increase the larger and older the ecosystem is (Cardinale et. al., 2012).

Increasing the supply of some ecosystem services can enhance the supply of others (forest restoration, for instance, may lead to improvements in carbon sequestration, runoff regulation, pollination, and wildlife), although there are also trade-offs (in this case with reduced capacity to provide food, for example).

There is some evidence to show that the effect that loss of biodiversity has on ecosystem processes is significant enough to be equivalent to other global factors which alter the environment. These include nutrient loading, air pollution, water pollution and acid rain (Cardinale et. al., 2012). However, more research is needed on this as the current evidence is not strong enough.

Supporting and provisioning services

Increased biodiversity helps to increase the potential of environments to produce food, building materials, drinking water and medicines (Díaz et. al., 2006), and areas with higher biodiversity have a higher level of productivity, a supporting ecosystem service that contributes to the ability of an ecosystem to produce food, wood or other physical products. (Balvanera et. al., 2006). Loss of species and reduction of gene pools reduce the efficiency by which communities can convert nutrients, water, light, prey and other resources into biomass, and evidence shows that that, in general, more diverse ecosystems have a more stable level of resource capture and biomass production (Cardinale et. al., 2012).

Loss of biodiversity at the top of the food web has an effect on the whole of the food web, right down to plants – losing as few as one or two top predators can reduce production of plant biomass as much as would be lost by turning a diverse community into a plant species monoculture and possibly even more than that (Cardinale et. al., 2012). Species which, if removed, would have a devastating effect on ecosystems are known as keystone species (Mills & Doak, 1993).

Humans have altered many ecosystems for certain provisioning services, especially food, fibre and biofuel production, has greatly simplified their structure, composition and functioning across scales; simplification has enhanced certain provisioning services, but reduced others, particularly regulating services; and simplification has led to major losses of biodiversity (4)

However, biodiversity doesn’t increase production in every ecosystem. Using evidence from multiple studies, it was found that 65% of 1,019 areas with high biodiversity had a lower production of biomass than the amount produced when the most productive species were grown as a monoculture. In addition to this, experiments on agricultural systems showed that increasing plant diversity only led to increased yield in 39% of the areas tested, and reduced the yield in 61% of the areas (Cardinale et. al., 2012).

Certain ecosystems may appear to have a higher productivity due to higher levels of biodiversity, but it is sometimes as a result of the presence of certain species which have a proportionally larger influence on productivity than some others (Cardinale et. al., 2012). For example, a study on the pollination of watermelon plants by twelve species of native bees in California showed that almost 80% of the pollination was done by two species and the remaining 10 species only made up 20% of the pollination, with several species making almost no contribution. As well as this, some of the bee species contributed more to the pollination than was expected in proportion to their abundance, and vice versa (6).

Regulating services

Increased plant diversity increases erosion control, a regulating ecosystem service, as soil erosion can be reduced by increased numbers of roots and mycorrhizae in the soil. (Balvanera et. al., 2006). Reduction in numbers of primary and secondary consumers can also increase risk of wildfire and spread of disease, and greatly alter vegetation structure in several different types of ecosystem (Cardinale et. al., 2012).

Positive biodiversity effects were found for most ecosystem properties associated with nutrient cycling services. Plant diversity had positive effects on decomposer activity and diversity, and both plant and mycorrhizal diversity increased nutrients stored in the plant compartment of the ecosystem. Increased native plant diversity can help to reduce the numbers of invasive species of both animals and plants present in an area (Balvanera et. al., 2006). Increased diversity of plant litter invertebrates regulates nitrogen and carbon mineralisation and other nutrient cycling processes in soils and litter (7) and these processes can also be affected by soil microbes and fungi. However, these organisms’ effects on nutrient cycling and decomposition are not as strong as the effects that other processes have (Cardinale et. al., 2012).

A higher diversity of microbes can cause harm to the ecosystem service of disease regulation. This is because a higher diversity creates more opportunities for the presence of disease-causing pathogens and increases the likelihood that drug-resistant strains of bacteria and viruses evolve (Cardinale et. al., 2012).

Cultural services

As well as providing measurable or physical products and services, high biodiversity also contributes to cultural services, including mental and physical health and wellbeing, economic resilience and security, spirituality and social relations. Humans have been converting natural ecosystems to human-dominated ecosystems for thousands of years, using biodiversity in order to benefit them. However, evidence is starting to appear that these benefits are beginning to have the cost of large losses of biodiversity and therefore degradation of supporting and regulating services. This in turn can cause loss of cultural services, which can cause associated effects such as localised poverty and mental health hotspots in these areas (MA, 2005).

The loss of biodiversity in certain ecosystems, particularly the loss of certain sacred species or areas, can reduce the spiritual benefit that the ecosystem gives to people. However, the opposite can also happen, where losing some diversity might cause people to appreciate the remaining species and areas more (MA, 2005).

Flagship or umbrella species: providing protection for wider communities and habitats (9)

Biodiversity as an ecosystem service

Alternatively, regarding biodiversity itself as an ecosystem service reflects an intrinsic value for biodiversity, whereby organisms have value that is by definition unquantifiable and therefore nontransactable. In practice, most people intuitively assign very different values to different groups of organisms, so that when biodiversity itself is seen as a service, it is particular groups, often charismatic ones, whose conservation is sought. Nevertheless, biodiversity has existence value to many people who wish it to continue to be there, irrespective of any direct experiences or benefits they derive from it. Also, this perspective does not reflect the values of biodiversity that are not based on its functional role in ecosystem processes. The ‘conservation perspective’ ignores the role of biodiversity in underpinning ecosystem processes, and usually focuses on a subset of biodiversity that includes charismatic species and those on threatened species lists. (9)

Genetic diversity of wild crop relatives is important for the improvement of crop strains, and the same will be true for biofuel crops and livestock. Therefore, both genetic diversity (or surrogates, such as wild species richness or phylogenetic diversity) and wild species diversity (implicitly including genetic and phylogenetic diversity) are final ecosystem services directly contributing to goods (Figure 1). In the case of these final ecosystem services, ecosystems could be specifically managed for the diversity of the desired biodiversity components. (9)

What further research is needed?

The amount of biodiversity loss that starts to have a significant effect on ecosystem functions and services is not currently known, although it is currently under research (4). In particular, research needs to be done in rarer or less studied ecosystems such as wetlands, peatland and others. Because of this lack of knowledge, policy-makers and scientists should be very cautious about their use of biodiversity (Balvanera et. al., 2006).

The effects of plant diversity on the performance and diversity of predatory insects or other animals that control pests require further investigation. (Balvanera et. al., 2006)

There is an urgent requirement for more detailed research into exactly how human activity alters levels of biodiversity. Usually, there are certain traits which cause certain organisms to be more likely to be lost from ecosystems than others, and these same factors are often the same ones that have the largest effect on ecosystem processes(4). Even in small or simple communities, these interactions are not understood well and it is very difficult to predict how other, more complex influences such as climate change, will affect them. (9)

The concept of ecosystem services is one which is expanding at a high rate, and the confusion surrounding the complex relationship between this and biodiversity is making it much more difficult to form useful, coherent policies about it. In order to solve this problem, scientists from many different backgrounds, including economists, biologists, ecologists, social sciences and others, will need to be brought together (9)