1. Rationalising Biodiversity Conservation in Dynamic Ecosystems
(RUBICODE)
Quantifying the contribution of organisms to the provision of ecosystem services
For further information contact Gary Luck (
Funded under the European Commission
Sixth Framework Programme
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2. Service-providing unit (SPU)
“The collection of organisms and their characteristics necessary to deliver a given ecosystem service at the level required by service beneficiaries.”
This presentation covers the RUBICODE approach to quantifying the contribution of organisms to providing ecosystem services. The key message is that we must identify and quantify the organisms and their characteristics that provide ecosystem services. We need to know how changes in these organisms impact on service provision if we are to understand the implications of change for human wellbeing. To address this issue, we introduce the concept of service-providing units or SPUs.
An SPU can be defined simply as the collection of organisms and their characteristics necessary to deliver a given ecosystem service at the level required by service beneficiaries.

3. Populations could be considered a fundamental unit of measure.
Loss of biodiversity is commonly characterised by species extinction rates.
Substantial change to ecosystems and the status of biodiversity occurs prior to species extinction.
Populations could be considered a fundamental unit of measure.
The relationship between biodiversity and human wellbeing is primarily a function of populations of species.
In 2003, Gary Luck published a paper with Gretchen Daily and Paul Ehrlich on population diversity and ecosystem services. In this paper the following arguments were presented. Loss of biodiversity is commonly characterised by species extinction rates. However, substantial change to ecosystems and the status of biodiversity occurs prior to species extinction. Therefore, it might be useful to consider populations as a fundamental unit of measure when assessing the status of biodiversity. The relationship between biodiversity and human wellbeing is primarily a function of populations of species.
In summary, it was argued that populations are important and we should be measuring change in populations (in addition to species) as an indicator of the status of biodiversity. Also, change in populations has implications for human wellbeing. If we accept these arguments – particularly in relation to the link between population change and human wellbeing, then we need to think carefully about how we define a population.

4. A taxonomy of populations
Evolutionary units - populations with independent evolutionary dynamics.
Demographic units - populations with independent demographic dynamics (e.g. fluctuate in size asynchronously).
Conservation units - depend on the associated conservation goals and may be formalized through concepts like MVPs and ESUs.
SPUs - defined by the service it provides to humanity, and the temporal and spatial extent of that service.
Populations can be defined in various ways. First, as evolutionary units, which are populations with independent evolutionary dynamics. As demographic units – populations with independent demographic dynamics (e.g. those that fluctuate in size asynchronously). As conservation units – which depend on the associated conservation goals and may be formalized through concepts like minimum viable populations. In the Luck et al. paper, a new approach was suggested to defining a population – the service providing unit. In short, the population is defined by the service it provides to humanity, and the temporal and spatial extent of the delivery of that service. They argued that defining a population through the service or services it provided to humanity was a more meaningful approach to determining how changes in the population would impact on human well-being.  

5. Service-providing unit (SPU)
“The collection of organisms and their characteristics necessary to deliver a given ecosystem service at the level required by service beneficiaries.”
Need to know
The sections of society that need/use the service.
The level at which it is required.
The organisms that provide the service (ecosystem service provider – ESP).
The characteristics of these organisms required to provide the service at the desired level (SPU).
The SPU definition assumes that the human need for an ecosystem process has been explicitly identified thereby defining it as a service (although it is important to note that detailed quantification of the level of need of a particular service is rarely done); it also assumes the rate of delivery of the service can vary, but needs to meet some base level defined by service beneficiaries; and that we can identify and quantify the organisms and their characteristics providing the service.
Put simply, we wish to know the sections of society that use the service and at what level is it required, what organisms provide the service (which we refer to as the ecosystem service providers or ESPs), and what characteristics of these organisms (e.g. density, distribution and functional traits) are required to provide the service at the desired level (which we define as the SPUs).
It is important to emphasise the difference in our use of the terms ecosystem service provider and service providing units. While these can be interpreted as being similar – the use of the word ‘unit’ is a deliberate attempt to focus attention on the need to quantify the characteristics of the collection of organisms required to deliver the service over and above simply identifying them. In some ways the SPU concept is analogous to the concept of minimum viable populations and evolutionary significant units in conservation biology and genetics.

6. Pest control in apple orchards
SPU =
Density of Parus major breeding pairs within the orchard that provide the service at the required level.
1-6 pairs/ha reduce caterpillar damage by up to 50%.
This example comes from papers published by Mols and Visser in 2002 and The authors document the capacity of Parus major – an insectivorous bird species – to provide a pest control service in apple orchards by substantially reducing caterpillar damage to the crop. The ESP as we define it is Parus major, the SPU is the density of breeding pairs within the orchard needed to deliver the service at the required level. At a density of 1-6 breeding pairs per 2 ha, caterpillar damage is reduced by up to 50% compared to control sites with no breeding pairs. The presence/density of breeding pairs is crucial since caterpillars form an important part of the bird’s diet during this period and are a preferred food item for nestlings. Therefore, it is vital that the breeding season coincides with caterpillar activity and stage of crop development, and that Parus major is able to breed within or near to apple orchards in sufficient densities. To reiterate, the SPU in this example is at least one breeding pair of Parus major every 2 ha within the apple orchard. However, it is not clear how service provision varies with incremental changes in breeding bird density. Also, Mols and Visser do not explicitly quantify the level of need for this service (by local landholders or the broader community), although they acknowledge that biological control of pests is increasing in importance because of changes in public attitudes, evolution of pesticide resistance in insects and legislative restrictions on pesticide use. Quantifying the level of need for a service is often poorly done or ignored in much of the literature, but its crucial if we are to determine the desirable characteristics of SPUs.
Mols & Visser J. Appl. Ecol. 39,
Mols & Visser PLoS One 2(2), e202.

7. { { Conceptual framework 1. IDENTIFICATION 2. QUANTIFICATION
Quantify the ecosystem service demand:
determine the net level of demand/need for the service
Quantify the service-providing unit (SPU):
determine the characteristics of organisms necessary for service provision
quantify the relationships between SPUs and service supply
quantify the components of biodiversity that support the SPU
Identify and value potential alternatives for providing the service
Evaluate options:
compare valuations and examine trade-offs
determine implications for biodiversity conservation
determine implications for policy and sustainable livelihoods
Define the ecosystem service:
identify the ecosystem service beneficiaries
identify the spatio-temporal scale of service delivery
identify the ecosystem service providers (ESPs)
1. IDENTIFICATION
2. QUANTIFICATION {
Value the service as provided by the SPU
3. APPRAISAL
This issue is addressed in more detail in this slide by putting the idea of SPUs in a broader conceptual framework for the study of ecosystem services. It outlines the steps that need to be undertaken to identify and quantify an ecosystem service using the SPU concept, although it is acknowledged that completion of all these steps is rarely achieved. The steps are presented in 3 stages.
Stage 1 Identification
It seems most logical to start this process by identifying the ecosystem service and the service beneficiaries – that is, those stakeholders who benefit directly (or indirectly) from the provision of the service. Of course, you can’t have a service without beneficiaries, but a clear delineation of who actually benefits from a given service is often ignored in the literature. We should also try to identify the spatial and temporal scale of service demand and the scale of service production. The latter delineates the boundaries for identifying the organisms that provide ecosystem services and the functional relationships occurring among them.
Stage 2 Quantification
The first step in quantification is determining the level of demand or need for a service. Once this is achieved, the requirements for service provision can be quantified, which leads to the delineation of the SPU. The relevant SPU characteristics which need quantifying will depend on the service in question and the organism(s) that supply it. This will be illustrated by a number of examples in the following slides.
 Stage 3 Appraisal
The third stage of the process involves the valuation of the service as provided by the SPU and potential alternatives, and the appraisal of implications for biodiversity conservation and policy.

8. Seed dispersal in urban park
Need defined by:
Cultural, recreational and biodiversity ‘value’ of park.
Eurasian Jay primary facilitator of acorn germination.
Estimate replacement cost of seed dispersal service.
SPU =
A minimum of 12 resident pairs of Eurasian Jay present each year for 14 years.
In this example by Hougner and colleagues, which describes the seed dispersal service provided by Eurasian Jays in oak forest in the National Urban Park of Stockholm, quantification of the need for a service is considered in three ways: First, they present general arguments of the cultural, recreational and biodiversity value of the park. They argue that oak forest makes a substantial contribution to these values in addition to oaks (Quercus spp.) being recognised as keystone species in the region. That is, they acknowledge a general need within the community for this park and for oak forest. Second, they show that the foraging and dispersal behaviour of Jays facilitates acorn germination to an extent much greater than any other animal species in the park. The Jay is needed to ensure the persistence of oaks. Third, they estimate the replacement cost of the seed dispersal service provided by Jays (i.e. the cost in dollars of seeding or planting oak trees by humans). Based on an estimated average value of 33,148 oak saplings per year (over a 14-year period) required for forest maintenance, Hougner and colleagues suggest that about 24 jays (or 12 pairs) would meet this requirement (this is a lower bound estimate and does not consider the need to buffer jay populations against environmental change). The ecosystem service provider is the Eurasian Jay; the service providing unit is a minimum of 12 resident jay pairs present each year for 14 years.
ctmsu.sytes.net
Hougner, C. et al Ecol. Econ. 59,

9. Service provision by functional groups
The ESP approach:
A species’ contribution to an aggregate service is defined by its effectiveness at performing the service and organism abundance. Changes in aggregate service result from changes in ESPs.
The SPU approach:
Argues for the need to understand more explicitly how characteristics manifested at the functional-group level (e.g. group composition) and for each member organism (e.g. population dynamics) impact on service provision.
So far, the examples have focused on single species, but an SPU might also be defined in terms of a functional group. Service provision by functional groups has received particular attention in the literature. Claire Kremen and colleagues have devoted substantial thought to this issue and it is acknowledged that the RUBICODE approach is similar in this context. Kremen et al. emphasised a species’ contribution to an aggregate service defined by its effectiveness at performing the service and organism abundance. Changes in aggregate service result from changes in ESPs. While similar, the SPU approach argues for the need to understand more explicitly how characteristics manifested at the functional-group level (e.g. group composition) and for each member organism (e.g. population dynamics) impact on service provision.

10. Pollination of watermelon
Up to 30 native bees pollinate watermelon.
Contribution to pollination varies across
years and within and among crops.
Diversity of native bee community
essential as the most functionally
important species can vary across time
and space.
SPU =
The composition of the functional group, the functional traits of each member, the population characteristics of each member, and appropriate spatial and temporal dynamics to deliver the service at the desired level.
Here, an example is shown to clarify the concept. Kremen and colleagues showed that up to 30 native bee species pollinate watermelon plants in agricultural regions of California. Species’ contribution to crop pollination can vary from one year to the next and within and among crops. Maintaining the diversity of the native bee community is essential because the most functionally important species in any given context can vary across time and space. The ESP as we define it is the pollinator functional group maintained at an appropriate diversity (e.g. group composition and abundance of individual members) with suitable traits aggregated from each species. The SPU is defined by the composition of the functional group (including the identity of each member), the functional traits of each member (which combined lead to the desired aggregate service), the population characteristics of each member (e.g. density) and appropriate spatial (e.g. distribution) and temporal (e.g. active during crop flowering) dynamics to deliver the service at the desired level.
That’s a lot to try to quantify!
Indeed, it is extremely challenging to identify, quantify and attempt to directly manage the desired characteristics of service providers when dealing with functional groups (especially with many members).
Kremen, C. et al PNAS 99,
Kremen, C. et al Ecol. Lett. 7,

11. Manage service delivery by protecting habitat that supports native bees.
About 40% cover within 2.4km should provide entire pollination service.
Native vegetation (~ 40%)
2.4km
watermelon crop
Kremen and colleagues recognised this by focussing on managing service delivery indirectly by quantifying the habitat needed to support the bee community. They calculated that approximately 40% cover of upland habitat within 2.4 km of a crop was required if the landholders wished to obtain their entire pollination service from native bees. Hence, it is possible to differentiate between the SPU – the assemblage of native bee pollinators, and its ‘supporting’ system(s) – the amount of upland habitat required to conserve bee populations that provide a given level of service. Quantifying the immediate support/habitat requirements of an SPU, especially for multi-species groups, may be a more feasible approach to managing service delivery because complex service – species interactions make it difficult to document the influence that change in any one species has on service provision. Concentrating on ‘supporting systems’ is already generally accepted in conservation, where protection measures based on the minimum habitat area required for the sustainability of populations are commonplace. This approach assumes a reasonable understanding of the relationships between supporting habitat, service providers and service delivery, yet our knowledge of habitat – service provider dynamics needs to be substantially improved.

12. Water regulation by forests
grail.cs.washington.edu
Quantified four factors that may influence water regulation: soil type; slope angle; vegetation type; and the area of each vegetation type.
This resulted in 90 categories of vegetation–soil–slope complexes, with water flow regulation differing substantially among complexes.
SPU =
The area of a given vegetation type occurring on a particular soil type at a particular slope angle required to provide the service to the level needed by service beneficiaries.
Here is a final, brief example with the SPU concept extended to ecological communities. Guo et al. (2000) demonstrated the capacity of terrestrial vegetation to regulate water flow in the Yangtze River watersheds with subsequent implications for the production of hydroelectricity. They quantified four key factors that may influence water regulation capacity: soil type, slope angle; vegetation type; and the area of each vegetation type. This resulted in 90 categories of vegetation–soil–slope complexes, with water flow regulation (and subsequently electricity production) differing substantially among complexes. The ecosystem service provider is terrestrial vegetation; the SPU is the area of a given vegetation type occurring on a particular soil type at a particular slope angle required to provide the service to the level needed by service beneficiaries.
na.unep.net
Guo et al. (2000) Ecol. Appl. 10,

13. Summary Ecosystem service Single species Multiple species
Seed dispersal
Community
Characteristics
Type, area, location
Water regulation
Population
Characteristics
Density, genetics, temporal and spatial dynamics
Functional group
Characteristics
Composition, traits, population characteristics
To summarise the key issues. When linking ecosystem services with the organisms that provide them, a useful starting point is the service itself. This will then guide appropriate explorations of service provider characteristics. That is, what we classify as an SPU will depend on the kind of service we are interested in and over what spatio-temporal context it exists. The important characteristics of SPUs will also change based on this classification. For example, the service of seed dispersal for a given plant or group of plants may be provided by a single key species or multiple species. If a single species we should focus at the population level and define the SPU based on relevant characteristics such as population density, temporal dynamics etc. If the service is provided by multiple species it would be classified as a functional group and the characteristics that would need to be determined to define the SPU would include functional group composition and trait measures, and population characteristics for each group member. Finally, if we choose another service such as water regulation, it is likely to be provided by multiple species comprising a community and we would be interested in characteristics such as type, area and location.
The complexity of these issues should be acknowledged and the next critical step is identifying simplified approaches to guide on-ground management. This is possible at all these levels and conceptual advances are being made. However, it is important to understand the level of complexity involved in the delivery of ecosystem services before moving on to exploring simplified rules-of-thumb or management approaches.

14. SPU – service relationships
Key phrase = “deliver a given ecosystem service at the level required by service beneficiaries”
Focuses attention on quantifying the contribution made by organisms to service delivery in relation to the needs of beneficiaries.
Avoids undue attention on organisms making insubstantial contributions (i.e. it identifies the key service providers).
Implies that if a collection of organisms are not contributing to service provision at the desired level they do not constitute an SPU (i.e. a threshold level of service delivery).
A key phrase in the definition of an SPU is “deliver a given ecosystem service at the level required by service beneficiaries”. The phrase focuses attention on quantifying the contribution made by organisms to service delivery in relation to the needs of beneficiaries. It also avoids undue attention being placed on organisms that make insubstantial contributions (i.e. it identifies the key service providers). Also, the implication is that if a collection of organisms are not contributing to service provision at the desired level they do not constitute an SPU. That is, there is a threshold level of service delivery above which a group of organisms are considered an SPU. Invoking this threshold is important because ecosystem services must be defined by both the contribution of service providers and the requirements of service beneficiaries. For example, the threshold may be a desired level of natural pest control that reduces the reliance on pesticides and results in crop yields at a given profit margin. However, thresholds are blunt instruments that potentially draw attention away from the need to understand how incremental changes in the characteristics of service providers impact on service delivery. The latter is very important because it helps to identify the trade-offs in obtaining a given outcome through ecosystem services or anthropogenic alternatives (e.g. the cost-benefits along a continuum of options for controlling pests based on various combinations of natural control from native and/or exotic species and pesticides).

15. SPU – service relationships
Native species
Exotic species
Human alternative
Given this, a series of curves can be envisaged that plot how changes in service provider dynamics or anthropogenic alternatives impact on a particular outcome (e.g. control of pests). We are particularly interested in the shape of the curve (or portion of the curve) related to service provision by native organisms as this illustrates the extent of their contribution and is most relevant to the relationship between the protection of ecosystem services and biodiversity conservation. In the first two examples shown here (a and b), native or native and exotic organisms contribute the entire service at the desired level and can be classified as SPUs. In the second two examples (c and d), native or exotic organisms do not provide the entire service (a human-derived alternative is required to meet service beneficiary needs – e.g. biocontrol + pesticide), but we may still wish to quantify the extent of the contribution and its form (e.g. a threshold relationship in the last example) and in some cases organisms may be classified as SPUs if their contribution has measurable benefits to service beneficiaries. d
Service provider dynamics

16. Species interactions Greenleaf & Kremen 2006. PNAS 103, 13890-13895.
Greenleaf & Kremen PNAS 103,
To understand the dynamics of SPUs it is important to recognise the impact of intra and interspecific species interactions on the delivery of services. These interactions can be positive, negative or neutral and include competition, commensalism, mutualism and predatory interactions. All have implications for service provision. For example, Perfecto and Vandermeer (2006) showed how the abundance of the scale insect and a mutualistic interaction with its attendant ant species influenced the degree of damage inflicted on coffee berries by the coffee berry borer. Greenleaf and Kremen (2006) found that behavioural interactions between native bees and the introduced honey bee enhanced the pollination efficiency of the honey bee on hybrid sunflower. Interactions that adversely affect service providers can negatively impact on the delivery of ecosystem services. This depends on the nature of the interaction and the characteristics of both the SPU and what we call the ecosystem service “antagoniser(s)”. For example, biocontrol agents that have played a critical role in controlling insecticide resistant red scale can be dramatically reduced by hyperparasitoids. Organisms that provide a service in one context may disrupt the provision of another (or the same) service in a different context. For example, the activities of beavers in cold-water streams can enhance the productivity of economically important fish species, but the same species are not favoured by beaver activities in warm-water streams. Alternatively, some service providers may promote the persistence of other species that provide additional ecosystem services (e.g. pollinators that pollinate plants that control soil erosion). An assessment of the service-providing value of organisms may need to consider trade-offs between service delivery, support of additional services and service disruption across a range of services.
It is easy to become bogged down in the complexity of these relationships. We argue that at the very least, we need to know something about the organisms and their characteristics that directly provide ecosystem services and what is required to support them. We do not necessarily need to know about every interaction that leads to the existence of SPUs – only enough to ensure their persistence.
Perfecto & Vandermeer Agriculture, Ecosystems and Environment 117,
Collen & Gibson Reviews in Fish Biology and Fisheries 10,

17. Coping with ecosystem dynamics
Functional groups and biodiversity:
When multiple species contribute to the same service, the stability of service provision should be buffered against fluctuations in the populations of the species comprising the effect functional group.
Assumes diversity of responses within functional group
Assumes quantitatively similar contributions to service provision
Implies functional replacement among species
Increased biodiversity is expected to secure continuation of ecosystem processes despite environmental variability.
A major problem in predicting the impacts of environmental changes on ecosystem services is the individualistic responses of service-providing organisms.
The value of the SPU concept is greatly enhanced if some consideration is given to ecosystem dynamics. Ecosystems are in constant flux and it is crucial to ensure that systems have the capacity to cope with likely changes if ecosystem services are to be maintained. This is especially true if environmental variation leads to species extinction or substantial fluctuations in population abundance. This issue has been explored in some depth when dealing with functional groups or a diversity of species. When multiple species contribute to the same ecosystem service, the stability of service provision should be, theoretically, buffered against fluctuations in the populations of the species comprising the effect functional group. This assumes a diversity of responses to environmental factors within functional group members that have a similar effect on the environment, and quantitatively similar contributions to service provision. It also implies functional replacement among species (i.e. when one species is lost another is able to fill its functional role). Compensatory effects may be most evident among groups of species with short generation times, high mobility, extreme population fluctuations and/or rapid turnover.
Increased biodiversity per se is expected to contribute positively to ecosystem stability and secure continuation of ecosystem processes despite environmental variability. However, recent evidence suggests that the buffering effects of biodiversity are dependent on the type of disturbance and may be non-existent in some circumstances.
A major problem in predicting the impacts of environmental changes on ecosystem services is the individualistic responses of service-providing organisms. Defining SPUs, where possible, in terms of functional groups based on their response traits and effect traits helps to circumvent this problem. The impact of environmental changes on service provision will then result from the overlap, co-occurrence and/or linkage among response and effect traits of SPUs.

18. Coping with ecosystem dynamics
Populations of key species:
Ensure life-history, population and genetic traits are appropriate to cope with likely changes in the environment.
Analogous to the MVP concept.
Must consider factors such as resilience to environmental variation, probability of persistence under future management scenarios, degrees of uncertainty and acceptable levels of risk for loss of the service.
If services are provided by populations of a key species, resilience may be maintained by ensuring that life-history, population and genetic traits are appropriate to cope with likely changes in the environment. This approach is analogous to the concept of minimum viable populations, which are generally defined from a conservation perspective (e.g. the number of individuals needed to reduce the chances of extinction of a population to an acceptable level). Indeed, by quantifying the links between organism characteristics and service provision the issue of minimum requirements for an SPU is largely unavoidable (i.e. the characteristics required to provide the service at the desired level). However, for the analogy to be appropriate, the definition of an SPU must consider factors such as resilience to environmental variation, probability of persistence under future management scenarios, degrees of uncertainty and acceptable levels of risk for loss of the service. For example, society may accept either a 1% or 5% probability of loss of an SPU within 100 years with the level of risk being determined by the consequences of service disruption (e.g. it may be less acceptable to lose a food production service compared to a recreational service).
Ensuring continuation of service provision via SPUs requires consideration of their resilience to change and the maintenance of future options. Clearly, resilience is a relative term dependent on the interactions between ecosystems and the magnitude and types of environmental and anthropogenic pressures. For ecosystem services, greater resilience is required if there are substantial cultural, social or economic implications of service provision failure. Sensitivity to environmental change and the implications of service disruption is a potential approach to prioritising the protection of ecosystem services (and their service providers).

19. Conceptual model + Positive interaction - Negative interaction
Although we have much to learn, the key relationships can be conceptualised into a model of service provision. Ecosystem services emanate from complex relationships between SPUs and the organisms or systems that support them. Several studies have demonstrated the role of indigenous habitat in supporting service providers such as native pollinators and quantified how changes in the area of, and/or distance to, this habitat may affect service provision. Also, SPUs can play a role in maintaining their support systems (e.g. bees pollinating wildflowers). Positive or negative species interactions can alter service provider – provision relationships. Environmental and land-use change is a major driver of ecosystem processes and services, and this can also impact on service beneficiary demand. Also, market, cultural and socio-economic factors and local, national and international policy will dictate the identity and requirements of service beneficiaries and drive environmental change. This has direct and indirect impacts on the demands made of ecosystems and the capacity of these systems to provide particular services. SPUs, whether key species, functional groups or ecological communities, are affected positively or negatively by environmental change and require a level of resilience that is sufficient to buffer against adverse impacts.
This model does not attempt to capture the complex social, cultural or financial trends that drive market or policy change (and their subsequent impact on the presence or type of service beneficiaries and their requirements). Also, it is context specific, focussing on the delivery of a single service by a designated SPU in a given land or seascape (e.g. we do not include circumstances where SPUs might provide other services or support service provision by other SPUs).
+ Positive interaction
- Negative interaction

20. Conclusions
SPUs:
Link organisms and their characteristics to service provision via the needs of beneficiaries.
Exist at various organisational levels.
Could be considered a threshold measure, but understanding incremental changes might still be important.
To conclude, the SPU concept links organisms and their characteristics to service provision via the needs of beneficiaries. SPUs exist at various organisational levels.
 The concept can be interpreted as a threshold measure, but it still may be important to understand incremental changes between service provider characteristics and the delivery of services.

21. Conclusions Species interactions are important for service provision.
Must consider ecosystem dynamics when managing for the persistence of SPUs and the continued supply of ecosystem services.
Ecological complexity + socio-economic complexity necessitates general approaches and assumptions.
It’s stating the obvious to say that species interactions influence service provision, but it is important that we understand the implications of key interactions. And importantly, we must address ecosystem dynamics if we are to ensure the continued supply of services. Ultimately, we are trying to comprehend interactions between complex ecological and socio-economic systems – and this necessitates generalities and assumptions – although we should try to understand as much of the complexity as possible before applying general approaches.
The issues covered in this presentation are certainly complicated, and understanding them appears to be a daunting challenge. But maybe it needn’t be. Ecologists have been studying interactions between organisms and their environment for decades. Research on ecosystem services is just asking what implications these interactions have for humanity.