Dégradation des Ecosystèmes

9. What are the most important uncertainties hindering decision-making concerning ecosystems?

• 9.1 What remains unknown about conditions and trends in ecosystems?
• 9.2 What are the problems linked to the use of scenarios?
• 9.3 What are the uncertainties in the response options?

The source document for this Digest states:

The MA was unable to provide adequate scientific information to answer a number of important policy questions related to ecosystem services and human well-being. In some cases, the scientific information may well exist already but the process used and time frame available prevented either access to the needed information or its assessment. But in many cases it is clear that either the data needed to answer the questions were unavailable or the knowledge of the ecological or social system was inadequate. We identify the following information gaps that, if adressed, could significantly enhance the ability of a process like the MA to answer policy-relevant questions posed by decision-makers (CWG, SWG, RWG, SGWG).

Source & ©: MA  Millennium Ecosystem Assessment Synthesis Report (2005),
Chapter 9, p.101

9.1 What remains unknown about conditions and trends in ecosystems?

The source document for this Digest states:

Conditions and Trends

• There are major gaps in global and national monitoring systems that result in the absence of well-documented, comparable, time-series information for many ecosystem features and that pose significant barriers in assessing conditions and trends in ecosystem services. Moreover, in a number of cases, including hydrological systems, the condition of the monitoring systems that do exist is declining.
  • Although for 30 years remote sensing capacity has been available that could enable rigorous global monitoring of land cover change, financial resources have not been available to process this information, and thus accurate measurements of land cover change are only available on a case study basis.
  • Information on land degradation in drylands is extremely poor. Major shortcomings in the currently available assessments point to the need for a systematic global monitoring program, leading to the development of a scientifically credible, consistent baseline of the state of land degradation and desertification.
  • There is little replicable data on global forest extent that can be tracked over time (C28.7);
  • There is no reasonably accurate global map of wetlands (C28.7).
• There are major gaps in information on nonmarketed ecosystem services, particularly regulating, cultural, and supporting services. (CWG)
• There is no complete inventory of species and limited information on the actual distributions of many important plant and animal species.
• More information is needed concerning:
  • the nature of interactions among drivers in particular regions and across scales;
  • the responses of ecosystems to changes in the availability of important nutrients and carbon dioxide;
  • nonlinear changes in ecosystems, predictability of thresholds, and structural and dynamic characteristics of systems that lead to threshold and irreversible changes (C28.7); and
  • quantification and prediction of the relationships between biodiversity changes and changes in ecosystem services for particular places and times (C28.7);
• There is limited information on the economic consequences of changes in ecosystem services at any scale and, more generally, limited information on the details of linkages between human well-being and the provision of ecosystem services, except in the case of food and water.
• There are relatively few models of the relationship between ecosystem services and human well-being (S13.5).

Source & ©: MA  Millennium Ecosystem Assessment Synthesis Report (2005),
Chapter 9, pp.101-102

9.2 What are the problems linked to the use of scenarios?

The source document for this Digest states:

Scenarios

• There is a lack of analytical and methodological approaches to explicitly nest or link scenarios developed at different geographic scales. This innovation would provide decision-makers with information that directly links local, national, regional, and global futures of ecosystem services in considerable detail.
• There is limited modeling capability related to effects of changes in ecosystems on flows of ecosystem services and effects of changes in ecosystem services on changes in human well-being. Quantitative models linking ecosystem change to many ecosystem services are also needed (S13.5).
• Significant advances are needed in models that link ecological and social processes, and models do not yet exist for many cultural and supporting ecosystem services.
• There is limited capability to incorporate adaptive responses and changes in human attitudes and behaviors in models and to incorporate critical feedbacks into quantitative models. As food supply changes, for example, so will patterns of land use, which will then feed back on ecosystem services, climate, and food supplies (S4).
• There is a lack of theories and models that anticipate thresholds that, once passed, yield fundamental system changes or even system collapse (S4).
• There is limited capability of communicating to nonspecialists the complexity associated with holistic models and scenarios involving ecosystem services, in particular in relation to the abundance of nonlinearities, feedbacks, and time lags in most global ecosystems (S4).

Source & ©: MA  Millennium Ecosystem Assessment Synthesis Report (2005),
Chapter 9, p.102

9.3 What are the uncertainties in the response options?

The source document for this Digest states:

Response Options

• There is limited information on the marginal costs and benefits of alternative policy options in terms of total economic value (including nonmarketed ecosystem services).
• Substantial uncertainty exists with respect to who benefits from watershed services and how changes in particular watersheds influence those services; information in both of these areas is needed in order to determine whether markets for watershed services can be a fruitful response option.
• There has been little social science analysis of the effectiveness of responses on biodiversity conservation (R5.4).
• There is considerable uncertainty with regards to the importance people in different cultures place on cultural services, how this changes over time, and how it influences the net costs and benefits of trade-offs and decisions.

Source & ©: MA  Millennium Ecosystem Assessment Synthesis Report (2005),
Chapter 9, p.102