Environmental Engineering Reference
In-Depth Information
21.1 INTRODUCTION: ANTICIPATING
THE FUTURE
early historical ranges of declining species has been
a viable restoration strategy (Burney & Burney
2007). Understanding the history of the development
of the current species assemblage has also helped
establish an expectation of the spatial and temporal
variation of the vegetation that cannot be accom-
plished with a static present-day perspective (Lind-
bladh
et al
. 2007). In some systems, however, even a
perspective that encompasses palaeo-ecological time
scales may prove unsustainable in the coming decades
due to the development of new combinations of envi-
ronmental factors (e.g. no-analogue climates) or new
barriers to species movement. Thus, the expectation
of the development of
novel ecosystems
, and the
shift in restoration goals for some target systems, from
those based on
reference
conditions to ones based
on ensuring maintenance of
ecosystem goods
and services
, also needs to be incorporated in res-
toration planning (Seastedt
et al
.
Ecologists have long recognized that ecological systems
are dynamic. Natural disturbances are widespread and
essential to the persistence of many ecosystems (Pickett
et al
. 1989). Superimposed on disturbances, changes
in climatic conditions have occurred throughout
Earth's history (Hessburg
et al
. 2005 ). Human activi-
ties have disrupted natural disturbance regimes either
by increasing frequency and intensity (e.g. fi re return
intervals, extreme climate events such as fl oods and
droughts, and pest outbreaks) or by decreasing fre-
quency and intensity (e.g. damming of rivers, and sup-
pression of fi res in grasslands and forests) (Dale
et al
.
2001 ; Franklin
et al
. 2005). In addition, human activi-
ties are affecting the speed at which these changes
occur; for instance, climate change is occurring faster
than ever recorded, nitrogen pollution has doubled
over the last half century and non-native species are
successfully establishing in ecosystems across the
globe (Vitousek
et al
. 1997 ; Chapin
et al
. 2006 ; see
Chapter 20 ).
As its name implies, restoration has traditionally
been viewed primarily as a means to reset the ecologi-
cal clock, with the goals ranging from returning the
system to particular reference assemblages to rehabili-
tating the system to provide a certain level of function
or service, such as erosion control or drinking water
quality. However, in this period of unprecedented envi-
ronmental change, the ecological clock is ticking more
and more rapidly, whether due to changes in climate,
shifts in land use or changes in fauna and fl oral diver-
sity (see Chapter 3). As restoration often has the aim
of directing the target system to a point along a trajec-
tory that allows for self-sustaining population, com-
munity and ecosystem processes, it is essential to
consider restoration in the context of anticipated
future environmental changes (Choi
et al
. 2008 ; Hobbs
& Cramer 2008 ).
Historical perspectives increase our understanding
of the dynamic nature of landscapes and provide a
frame of reference for assessing modern patterns and
processes (Swetnam
et al
. 1999 ; Jackson & Hobbs
2009). Although many future changes may not have
historical analogues, a historical perspective can help
design or steer emerging systems to encompass a
greater spectrum of natural variability inherent in the
system or under future climate change. For instance,
creating new populations in formerly much larger,
2008 ;
see
also
Chapter 3 ).
In this chapter, we address how restoration ecolo-
gists and practitioners can apply theory on evolution-
ary and community dynamics to anticipate and
incorporate future - and largely uncertain - environ-
mental changes. We focus on how local and regional
processes may infl uence population and community
dynamics over time, in turn affecting how we should
manage and restore biodiversity and ecosystem serv-
ices. Accordingly, we start with the assumption that
the initial stages of a restoration project were largely
successful - that a particular reference assemblage or
a level of function or service in an analogous undis-
turbed area has been established. With this as a start-
ing point, we suggest additional considerations for
restoration projects with the expectation of future evo-
lutionary and ecological change, as well as how to set
goals and plan
interventions
for restoration without
aiming at a static, and in many cases unrealistic,
endpoint.
We fi rst discuss the evolutionary mechanisms that
determine whether species persist in altered environ-
ments, and secondly, the community-level mecha-
nisms that may shift when species differ in their ability
to respond to altered system dynamics. Next, we
discuss the potential larger scale processes, specifi cally
gene fl ow and dispersal, to help or hinder persistence
of communities, and fi nally, the importance of main-
taining diversity at all levels - genotypes, species
and functional groups - for restoration in a changing
world.
