Managing endangered species

Temperature and moisture also strongly global climate influence the life cycle of butterflies.

change: will nature

, . , Beaumont and Hughes (2002) used the reserves be in the approach applied to spiny acacia above to predict the effect of climate change on the distribution of 24 Australian butterfly species. Under even a moderate set of future conditions (temperature increase of 0.8—1.4°C by 2050), the distributions of 13 of the species decreased by more than 20%. Most at risk are those, such as Hypochrysops halyetus, that not only have specialized food-plant requirements but also depend on the presence of ants for a mutualistic relationship. The models suggest that H. halyetus, which is restricted to coastal heathland in Western Australia, will lose 58-99% of its current climatic range. Moreover, less than 27% of its predicted future distribution occurs in locations that it

Figure 7.31 (right) The predicted distribution of spiny acacia in Australia on the basis of (a) current climate, (b) a scenario with an average 2°C increase and a 10% increase in precipitation, and (c) a 2°C increase and a 10% decrease in precipitation. The predicted distributions in (b) and (c) also assume an increased efficiency of water use by spiny acacia because of a fertilizing effect of increased atmospheric carbon dioxide. (After Kriticos et al., 2003.)

Species category

Current climate

Restricted to the reserve

Cephalocereus columna-trajani 138

Ferocactus flavovirens 317

Mammillaria huitzilopochtli 68

Mammillaria pectinifera 5,130

Pachycereus hollianus 175

Polaskia chende 157

Polaskia chichipe 387

Intermediate distribution

Coryphantha pycnantha 1,367

Echinocactus platyacanthus f. grandis 1,285

Ferocactus haematacanthus 340

Pachycereus weberi 2,709

27 532 21 1,124 87 83 106

0 100 0

486 0 76 10

1,088 230 1,220 1,468

807 1,148 170 1,012

Table 7.10 The potential core distributions (km2) of cacti under current climatic conditions and for three climate change scenarios for Mexico. Species in the first category of cacti are currently completely restricted to the 10,000 km2 Tehuacan-Cuicatlan Biosphere Reserve. Those in the second category have a current range more or less equally distributed within and outside the reserve. The current ranges of species in the final category extend widely beyond the reserve boundaries. (After Tellez-Valdes & Davila-Aranda, 2003.)

Widespread distribution Coryphantha pallida Ferocactus recurvus Mammillaria dixanthocentron Mammillaria polyedra Mammillaria sphacelata Neobuxbaumia macrocephala Neobuxbaumia tetetzo Pachycereus chrysacanthus Pachycereus fulviceps

10,237 3,220 9,934 10,118 3,956 2,846 2,964 1,395 3,306

5,887 3,638 7,126 5,512 5,440 4,943 1,357 1,929 5,405

2,920 151 3,162 2,611 2,580 1,964 395 382 1,071

currently occupies. This result highlights a general point for managers: regional conservation efforts and current nature reserves may turn out to be in the wrong place in a changing world.

Tellez-Valdes and Davila-Aranda (2003) explored this issue for cacti, the dominant plant form in Mexico's Tehuacan-Cuicatlan Biosphere Reserve. From knowledge of the biophysical basis of the distribution of current species and assuming one of three future climate scenarios, they predicted future species' distributions in relation to the location of the reserve. Table 7.10 shows how the potential ranges of species contracted or expanded in the various scenarios. Focusing on the most extreme scenario (an average temperature increase of 2.0°C and a 15% reduction in rainfall), it is evident that more than half of the species that are currently restricted to the reserve are predicted to go extinct. A second category of cacti, whose current ranges are almost equally within and outside the reserve, are expected to contract their ranges, but in such a way that their distributions become almost completely confined to the reserve. A final category, whose current distributions are much more widespread, also suffer range contraction but in future they are expected to still be distributed within and outside the reserve. In the case of these cacti, then, the location of the reserve seems to cater adequately for potential range changes.

We noted above that the performance of the butterfly Hypochrysops halyetus depends not just on its own physiology and behavior but also on a mutualistic interaction with ants. Moreover, while cactus distributions are fundamentally dependent on appropriate physicochemical conditions, they are also certain to be influenced by competition for resources with other plants and by their interactions with the species that feed upon them. We now turn our attention, in the second section of the book, to the ecology of interacting populations.

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