Environmental Engineering Reference
In-Depth Information
Aquatic systems feature poorly in existing conservation templates,
although there is evidence that marine biodiversity may be at least as
threatened as (Dulvy et al., 2003) and freshwater biodiversity even more
threatened (McAllister et al., 1997) than that on land (Baillie et al.,
2004). Only one conservation prioritization explicitly incorporates aquatic
systems (Olson and Dinerstein, 1998). The irreplaceability dimension has
been particularly overlooked in the seas, with the traditional emphasis of
marine conservation being on species richness (Briggs, 2002) despite little
correspondence between marine species richness and endemism (Hughes
et al., 2002; Price, 2002). Nevertheless, the most comprehensive study yet,
albeit restricted to tropical coral reef ecosystems, identii ed ten priority
regions based on endemism and threat (Roberts et al., 2002). Eight of
these regions lie adjacent to priority regions highlighted in Figure 2.4,
raising the possibility of correspondence between marine and terrestrial
priorities despite the expectation that surrogacy of conservation priorities
will be low between dif erent environments (Reid, 1998). Ef orts to iden-
tify freshwater priorities lag further behind, although initial studies reveal
a highly uneven distribution of freshwater i sh endemism at regional
(Darwall et al., 2005) and global (Mittermeier et al., 2004) scales.
Most measurement of irreplaceability is species-based, raising the
concern that phylogenetic diversity may slip through the net of global
conservation priorities (Mace et al., 2000; Jepson and Canney, 2001;
Brummitt and Lughadha, 2003; Kareiva and Marvier, 2003). However,
analyses for mammals (Sechrest et al., 2002) and birds (Brooks et al., 2005)
i nd that priority regions represent higher taxa and phylogenetic diversity
better than would be predicted by the degree to which they represent
species. Islands such as Madagascar and the Caribbean hold especially
high concentrations of endemic genera and families (Mittermeier et al.,
2004). A heterodox perspective argues that the terminal tips of phyloge-
netic trees should be higher priorities than deep lineages (Erwin, 1991). In
any case, the balance of work implies that even if phylogenetic diversity
is not explicitly targeted for conservation, global prioritization based on
species provides a solid surrogate for evolutionary history.
That global conservation priority regions capture phylogenetic history
does not necessarily mean they represent evolutionary process (Mace
et al., 2000; Myers and Knoll, 2001; Smith et al., 2001). For example,
transition zones or 'biogeographic crossroads', frequently overlooked by
conservation prioritization, could be of particular importance in driving
speciation (Smith et al., 1997; Spector, 2002). On the other hand, the scale
of global conservation priorities is often coarse enough to capture the
transitions necessary in facilitating evolutionary processes, such as resili-
ence to climate change
(Midgley et al., 2001). There is also evidence that
