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Dégradation des Ecosystèmes

6. Why are both global and sub-global assessments of ecosystem change useful?

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    The MA included a sub-global assessment component to assess differences in the importance of ecosystem services for human well-being around the world (SG.SDM). The Sub-global Working Group included 33 assessments around the world. These were designed to consider the importance of ecosystem services for human well-being at local, national, and regional scales. The areas covered in these assessments range from small villages in India and cities like Stockholm and São Paulo to whole countries like Portugal and large regions like southern Africa. In a few cases, the sub-global assessments were designed to cover multiple nested scales.

    For example, the Southern Africa study included assessments of the entire region of Africa south of the equator, of the Gariep and Zambezi river basins in that region, and of local communities within those basins. This nested design was included as part of the overall design of the MA to analyze the importance of scale on ecosystem services and human well-being and to study cross-scale interactions. Most assessments, however, were conducted with a focus on the needs of users at a single spatial scale—a particular community, watershed, or region.

    The scale at which an assessment is undertaken significantly influences the problem definition and the assessment results (SG.SDM). Findings of assessments done at different scales varied due to the specific questions posed or the information analyzed. Local communities are influenced by global, regional, and local factors. Global factors include commodity prices (global trade asymmetries that influence local production patterns, for instance) and global climate change (such as sea level rise). Regional factors include water supply regimes (safe piped water in rural areas), regional climate (desertification), and geomorphological processes (soil erosion and degradation). Local factors include market access (distance to market), disease prevalence (malaria, for example), or localized climate variability (patchy thunderstorms). Assessments conducted at different scales tended to focus on drivers and impacts most relevant at each scale, yielding different but complementary findings. This provides some of the benefit of a multiscale assessment process, since each component assessment provides a different perspective on the issues addressed.

    Although there is overall congruence in the results from global and sub-global assessments for services like water and biodiversity, there are examples where local assessments showed the condition was either better or worse than expected from the global assessment (SG.SDM). For example, the condition of water resources was significantly worse than expected in places like São Paulo and the Laguna Lake Basin in the Philippines. There were more mismatches for biodiversity than for water provisioning because the concepts and measures of biodiversity were more diverse in the sub-global assessments.

    Drivers of change act in very distinct ways in different regions (SG7.ES). Though similar drivers might be present in various assessments, their interactions—and thus the processes leading to ecosystem change—differed significantly from assessment to another. For example, although the Amazon, Central Africa, and Southeast Asia in the Tropical Forest Margins assessment have the same set of individual drivers of land use change (deforestation, road construction, and pasture creation), the interactions among these drivers leading to change differ. Deforestation driven by swidden agriculture is more widespread in upland and foothill zones of Southeast Asia than in other regions. Road construction by the state followed by colonizing migrant settlers, who in turn practice slash-and-burn agriculture, is most frequent in lowland areas of Latin America, especially in the Amazon Basin. Pasture creation for cattle ranching is causing deforestation almost exclusively in the humid lowland regions of mainland South America. The spontaneous expansion of smallholder agriculture and fuelwood extraction for domestic uses are important causes of deforestation in Africa.

    The assessments identified inequities in the distribution of the costs and benefits of ecosystem change, which are often displaced to other places or future generations (SG.SDM). For example, the increase in urbanization in countries like Portugal is generating pressures on ecosystems and services in rural areas. The increase in international trade is also generating additional pressures around the world, illustrated by the cases of the mining industries in Chile and Papua New Guinea. In some situations, the costs of transforming ecosystems are simply deferred to future generations. An example reported widely across sub-global assessments in different parts of the world is tropical deforestation, which caters to current needs but leads to a reduced capacity to supply services in the future.

    Declining ecosystem trends have sometimes been mitigated by innovative local responses. The “threats” observed at an aggregated, global level may be both overestimated and underestimated from a sub-global perspective (SG.SDM). Assessments at an aggregated level often fail to take into account the adaptive capacity of sub-global actors. Through collaboration in social networks, actors can develop new institutions and reorganize to mitigate declining conditions. On the other hand, sub-global actors tend to neglect drivers that are beyond their reach of immediate influence when they craft responses. Hence, it is crucial for decision-makers to develop institutions at the global, regional, and national levels that strengthen the adaptive capacity of actors at the sub-national and local levels to develop context-specific responses that do address the full range of relevant drivers. The Biodiversity Management Committees in India are a good example of a national institution that enables local actors to respond to biodiversity loss. This means neither centralization nor decentralization but institutions at multiple levels that enhance the adaptive capacity and effectiveness of sub-national and local responses.

    Multiscale assessments offer insights and results that would otherwise be missed (SG.SDM). The variability among sub-global assessments in problem definition, objectives, scale criteria, and systems of explanation increased at finer scales of assessment (for example, social equity issues became more visible from coarser to finer scales of assessment). The role of biodiversity as a risk avoidance mechanism for local communities is frequently hidden until local assessments are conducted (as in the Indian local, Sinai, and Southern African livelihoods studies).

    Failure to acknowledge that stakeholders at different scales perceive different values in various ecosystem services can lead to unworkable and inequitable policies or programs at all scales (SGWG). Ecosystem services that are of considerable importance at global scales, such as carbon sequestration or waste regulation, are not necessarily seen to be of value locally. Similarly, services of local importance, such as the cultural benefits of ecosystems, the availability of manure for fuel and fertilizer, or the presence of non-timber forest products, are often not seen as important globally. Responses designed to achieve goals related to global or regional concerns are likely to fail unless they take into account the different values and concerns motivating local communities.

    There is evidence that including multiple knowledge systems increases the relevance, credibility, and legitimacy of the assessment results for some users (SG.SDM). For example, in Bajo Chirripó in Costa Rica, the involvement of nonscientists added legitimacy and relevance to assessment results for a number of potential users at the local level. In many of the sub-global assessments, however, local resource users were one among many groups of decision-makers, so the question of legitimacy needs to be taken together with that of empowerment.

    Integrated assessments of ecosystems and human well-being need to be adapted to the specific needs and characteristics of the groups undertaking the assessment (SG.SDM, SG11.ES). Assessments are most useful to decision-makers if they respond to the needs of those individuals. As a result, the MA sub-global assessments differed significantly in the issues they addressed. At the same time, given the diversity of assessments involved in the MA, the basic approach had to be adapted by different assessments to ensure its relevance to different user groups. (See Box 6.1.) Several community-based assessments adapted the MA framework to allow for more dynamic interplays between variables, to capture fine-grained patterns and processes in complex systems, and to leave room for a more spiritual worldview. In Peru and Costa Rica, for example, other conceptual frameworks were used that incorporated both the MA principles and local cosmologies. In southern Africa, various frameworks were used in parallel to offset the shortcomings of the MA framework for community assessments. These modifications and adaptations of the framework are an important outcome of the MA.

    Source & ©: MA  Millennium Ecosystem Assessment Synthesis Report (2005),
    Chapter 6, pp.84-87

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