Landscape management - Ecological Applications: Toward a Sustainable World - page 298

Fig. 10.17 Percent
change in the Walnut
Creek Catchment Area
for each scenario
(Production, Water
Quality and Biodiver-
sity, compared to the
current situation) in
water quality measures
(sediment, nitrate
concentration), an
economic measure
(farm income in the
catchment as a whole),
a measure of farmer
preference for each
scenario (based on
farmer ratings of images
of what the land cover
would look like under
each scenario) and two
biodiversity measures
(plant and vertebrate).
The Biodiversity
scenario ranks
consistently above the
Production scenario,
and the Water Quality
scenario ranks above
the Production scenario
in all but economic
profi tability. (After
Santelmann et al.,
2004.)

Production
Water quality
Biodiversity

200

150

100

50

0

-50

-100

surprising that the Biodiversity scenario ranks highest for improvements in plant
and animal biodiversity. Much more surprising is the fi nding that the land-use and
management practices required by the Biodiversity scenario are nearly as profi table
as current practices. The Biodiversity scenario also ranks highest in terms of accept-
ability to farmers (based on farmer ratings of images of what the land cover would
look like under each scenario), and provides water quality improvements similar in
magnitude to those in the Water Quality scenario. It seems that despite the slightly
higher profi tability of the Production scenario, farmers would not be unhappy with
a Biodiversity strategy that provides the greatest benefi ts to the community at large
in terms of biodiversity and ecosystem services.

Landscapes, metapopulations and metacommunities
Landscape ecology takes a broad view, dealing with the way individuals, populations
and communities behave in the patchwork of habitats that occur in a region.
Where a species exists as a metapopulation (a collection of subpopulations linked
by dispersal), its dynamics are strongly infl uenced by the rate of extinction of indi-
vidual subpopulations, and the rate of colonization - by dispersal from existing
subpopulations - of habitable but uninhabited patches. It is not unusual for an
endangered species to exist as a series of subpopulations in a metapopulation. And
even where only a single 'subpopulation' remains, the fi rst management step may
be to increase the size of the population so that it can be subdivided into a meta-
population, moving away from the all-eggs-in-one-basket syndrome.
By analogy with metapopulations, when the whole community of species is viewed
at the landscape scale, a metacommunity may be discerned - a set of local commu-
nities that are linked by dispersal of multiple, potentially interacting species. 'Island
Biogeography Theory', equally applicable to oceanic islands and to 'habitat islands',
holds that there is a continual turnover of species - because of species extinction
and colonization events - but that a balance is achieved. Larger islands tend to have
a higher equilibrium number of species, while more isolated islands have a lower

Summary