Vulnerabilities - Terrestrial biodiversity

Extinction debt of high-mountain plants

The extremes of possible climate-change-driven habitat range size reductions are commonly based on two assumptions: either species instantaneously adapt their ranges to any change in the distribution of suitable sites (`unlimited dispersal' scenario), or they are unable to move beyond the initially occupied sites (`no dispersal' scenario) (5). In addition to these static, niche-based model predictions, a so-called hybrid model was used that couples niche-based projections of geographical habitat shifts with mechanistic simulations of local demography and seed dispersal (based on regional circulation model projections and the A1B climate change scenario) (6).

Averaged across 150 species in the Alps, the hybrid model simulations indicate that by the end of the twenty-first century these high mountain plants will have lost 44-50% of their present alpine habitat ranges under high and low values of demographic and dispersal parameters, respectively (6).

The hybrid model indicates that the opposing effects of delayed local population extinctions and lagged migration rates will result in less severe twenty-first-century range reductions of alpine plants than expected from static, niche-based model predictions. However, these apparently `optimistic' forecasts include a large proportion of remnant populations under already unsuitable climatic conditions (6). The persistence of such remnant populations creates an extinction debt that will have to be paid later unless species manage to adapt phenotypically or genetically to the changing climate (7) and to the likely associated alterations in their biotic environments (8).

Most importantly, the hybrid model results consistently caution against drawing overoptimistic conclusions from relatively modest range contractions observed during the coming decades, as these are likely to mask more severe longer-term warming effects on mountain plant distribution (6).

Vulnerabilities - Fresh water and wetlands biodiversity

Glacier-fed rivers

As a result of the apparent `low' biodiversity, and minimal knowledge regarding the distribution of alpine aquatic species, glacier-fed rivers have received negligible attention from conservationists (2). The rapid shrinking of glaciers results in a reduction in glacial meltwater contribution to river flow in many glacierized catchments (3). These changes potentially affect the biodiversity of specialized glacier-fed river communities (4).

Research has shown that 11–38% of the regional species pools in study regions in Ecuador, the Alps and Alaska, including endemics, can be expected to be lost following complete disappearance of glaciers in a catchment, and steady shrinkage is likely to reduce local richness at downstream reaches where glacial cover in the catchment is less than 5–30% (2). Extinction will probably greatly exceed the few known endemic species in glacier-fed rivers.

Adaptation strategies

In the national strategy of France the following adaptation measures are recommended (1):

Integrate the challenges of climate change into existing biodiversity conservation and management policies:

• reinforce the efforts to reduce the pressures on biodiversity other than climate change, in order to increase the resilience of ecosystems;
• ensure the integration of biodiversity-related problems into all general and sectoral policies on mitigation and adaptation to climate change in order to maximise the cobenefits;
• protected spaces (including Regional Natural Parks), land projects, ecological and connectivity networks.

Integrate new principles and tools into these same public policies:

• promote adaptive management;
• reconcile the conservation of a maximum of species with a functional approach in order to ensure the properties of ecosystems and the dependent services are maintained;
• draw up a decision tree enabling the most suitable intervention or non-intervention methods to be defined.

Promote integrated governance:

• propose a general governance scheme organising existing steering and presentation devices to manage all dimensions of biodiversity and ecosystem services over suitable space and time scales.

Inform and mobilise all players:

• promote the strategies/measures that involve localusers and players;
• develop social science research into accepting adaptation measures.

References

The references below are cited in full in a separate map 'References'. Please click here if you are looking for the full references for France.

1. ONERC (2007/2009)
2. Jacobsen et al. (2012)
3. Barnett et al. (2005); Milner et al. (2009), both in: Jacobsen et al. (2012)
4. Brown et al. (2007), in: Jacobsen et al. (2012)
5. Thuiller et al. (2008), in: Dullinger et al. (2012)
6. Dullinger et al. (2012)
7. Bradshaw and Holzapfel (2006), in: Dullinger et al. (2012)
8. Brooker and Plant (2006), in: Dullinger et al. (2012)