Geoscience Reference
In-Depth Information
ICE ALGAE KELP PHYTOPLANKTON
Other
zooplankton
Ice
amphipods
Other
bivalves
Copepod
MYA
Other
amphipods
Other gelatinous
zooplankton
Other
benthos
Chaetognaths
Arctic cod
Parathemisto
Walrus
Guillemots
Kittiwakes
Ringed
seal
Bearded
seal
Fulmars
Murres
Norwal
Beluga
Harp seal
Killer
whales
Gulls
Polar bears
Humans
Energy flows
Energy flows dependent on arctic cod
Figure 24.20 Energy flows through the marine ecosystem of Lancaster Sound, Arctic Canada.
Source: Adapted from Welch et al. (1992)
effects ( Plate 24.19 ). The biogeography of polar and alpine
environments means that human presence is more likely
to have negative effects on ecological integrity as habitat
loss and degradation will impact more severely on species
which are already limited in their ranges.
Low productivity in polar and alpine habitats means
that the carrying capacities of such habitats are more
limited than in temperate regions. Lower biodiversity and
reduced availability of resources and habitats lead to
populations quickly exceeding the habitat's carrying
capacity. Some species may be able to counter such threats
by migration to new habitats, somewhat in the manner of
current seasonal migrations. However, species already at
the upper margins of their range, whether polar or
altitudinal, will have little opportunity to migrate, either
permanently and seasonally, to areas which are becoming
increasingly unsuitable through climate warming and
human disturbance. Temperate species can track climate
change by moving northwards,
allowing. Such changes have already been documented by
research by Walker et al. (2002), who predict the
northward expansion of temperate species, less likely to
be exposed to their lower thermal limits. Similarly
in alpine regions, upward expansion of the ranges of
montane species gradually displaces alpine species. Such
displacements could lead to the extirpation of alpine
species already at their altitudinal limits, with subsequent
elimination of interacting species and potential loss of
dependent mammalian species. Compared with temper-
ate ecosystems, polar and alpine ecosystems exhibit lower
productivity, smaller biodiversity, less resistance to change,
lower resilience to recover, and greater temporal and
spatial variation in the abundance of their constituent
populations (see also Chapter 28).
Large fluctuations in the population size of Arctic land
and marine mammals are a clear sign of young and
unstable ecosystems (see Chapter 22). Charles Elton
studied the records of the Hudson's Bay Company and
dispersal capability
 
 
Search WWH ::




Custom Search