Environmental Engineering Reference
In-Depth Information
Table 11.2
The core
distributions (km
2
) of
cacti in Mexico under
current conditions and
as predicted for three
climate change
scenarios. Species in
the fi rst category of
cacti are currently
completely restricted to
the 10,000 km
2
Tehuac án-Cuicatlán
Biosphere Reserve.
Those in the second
category have a current
range more or less
equally distributed
inside and outside the
reserve. The current
ranges of species in the
fi nal category extend
widely beyond the
reserve boundaries.
(After Téllez-Valdés &
Dávila-Aranda, 2003.)
+
1.0ºC
+
2.0ºC
+
2.0ºC
Species category
Current
−
10% rain
−
10% rain
−
15% rain
Restricted to the reserve
Cephalocereus columna-trajani
138
27
0
0
Ferocactus fl avovirens
317
532
100
55
Mammillaria huitzilopochtli
68
21
0
0
Mammillaria pectinifera
5,130
1,124
486
69
Pachycereus hollianus
175
87
0
0
Polaskia chende
157
83
76
41
Polaskia chichipe
387
106
10
0
Intermediate distribution
Coryphantha pycnantha
1,367
2,881
1,088
807
Echinocactus platyacanthus f. grandis
1,285
1,046
230
1,148
Ferocactus haematacanthus
340
1,979
1,220
170
Pachycereus weberi
2,709
3,492
1,468
1,012
Widespread distribution
Coryphantha pallida
10,237
5,887
3,459
2,920
Ferocactus recurvus
3,220
3,638
1,651
151
Mammillaria dixanthocentron
9,934
7,126
5,177
3,162
Mammillaria polyedra
10,118
5,512
3,473
2,611
Mammillaria sphacelata
3,956
5,440
2,803
2,580
Neobuxbaumia macrocephala
2,846
4,943
3,378
1,964
Neobuxbaumia tetetzo
2,964
1,357
519
395
Pachycereus chrysacanthus
1,395
1,929
872
382
Pachycereus fulviceps
3,306
5,405
2,818
1,071
small proportion of the locations where vernal pools occur. The protection of vernal
pool dwellers, such as fairy shrimps (
Branchinecta
spp.), is thus far from assured
even under current climatic conditions.
One of the key physical parameters that determine the success of fairy shrimps
is
F
max
- the annual average number of days of continuous inundation of a temporary
pond. The fairy shrimps are restricted to temporary ponds that remain inundated
long enough for the shrimps to mature and breed, but dry up soon enough to prevent
the build up of their predators. Figure 11.14b shows the geographical variation in
F
max
under current climatic conditions, while Figure 11.14c and d show changes to
F
max
under two climate change scenarios. Both global climate models predict Cali-
fornia will become wetter, but there is less certainty about whether local tempera-
tures will decrease (Figure 11.14c) or increase (Figure 11.14d).
Species of fairy shrimp at risk of extinction have different niche requirements (in
terms of
F
max
, etc.) and thus different distributions across California. The current
ranges of three of the species are superimposed on Figure 11.14b. The predicted
effects of changed inundation period on each species can be used to identify those
that will be adequately protected by current reserves and to assist managers to select
new protected areas to provide for the needs of fairy shrimp biodiversity overall.
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