Download Review of pattern and process

Until just two decades ago conservation efforts were being dealt with in an insular
framework. Protected Areas were mostly isolated and protecting from the destructive
effects surrounding man-made developments. This led to the following statement that
National Parks…
"have not drawn us into a more thoughtful relationship with our habitat, They have not
taught us that land is to be used frugally and with good sense. They have encouraged
us to believe that conservation is merely a system of trading environmental write-offs
against large protected areas. They more than failed; in fact they have become a
symptom of the problem"
(Van Tighem 1986).
This approach was paralleled by an approach where a single umbrella, or charismatic
species, was identified, and natural areas put aside for its conservation (e.g. Mountain
Gorilla). Neither the highly protected conservation area nor the species-approach were
effective (Angenmeir and Karr 1994). Even the usefulness of core concepts such as
climax has little relevance for conservation practice (Holdgate 1996).
Increasingly people are seeing the value of ecosystems as producing indispensable
benefits for the economy, public health and general welfare of human beings (Daily
1977), and this has led to concept of goods and services being derived from natural
ecosystems. The following are all significant goods and services (see Cairns 1996):
1) regulation of the composition of atmospheric gases
2) regulation of the hydrological cycle
3) control of erosion
4) maintenance of the energy flow through the ecosystem
5) maintenance of biogeochemical cycles
6) transfer of nutrients
7) pollination of plants
8) biological control of populations
9) preservation of biological diversity
10) storage and supply of water
11) production of food and animal materials, and
12) development of human habitat for leisure and culture.
The concept that one needs to have areas with minimum to no human disturbance is
increasingly being questioned as we realise that semi-natural (i.e. managed)
ecosystems can contained large quantities of biodiversity. Also there is a greater
realisation that ecosystems require some form of disturbance to ensure that competitive
dominance can occur. Consequently some disturbance and even exploitation can
actually occur (Connell 1978). Conservation practice is now seeking to determine
optimal combinations of natural, semi-natural and urban artificial ecosystems in an
integrated system that ensures environmental services are guaranteed. It is now
recognised that the landscape consists of repeated ecosystems and a mosaic of patches
that maintain functional processes (Forman 1995). Ecological integrity, therefore,
requires the representation of a range of indigenous species and ecological functions
(with their scope of natural variability), regardless of the local scale of the ecosystem.
The concept of sustainability is intimately linked with the health of the ecosystem and
consequently the concept of sustainable landscape is one in which it is considered that
there is good environmental health.
The birth of landscape ecology has contributed to conservation biology since it attempts
to analyse the role played by each element of the landscape by taking into consideration
its contribution to the health of the ecosystem. Landscape ecology can be considered
the study of interactions between landscape patterns and ecological processes;
specifically the patterns on the flows of water, energy, nutrients, and biota (Turner 1989).
The major contributions of landscape ecology are the identification of the relationships
between the structure of landscape and the relevant ecological process, with respect to
maintaining the delivery of environmental goods and services. Secondly it provides a
hierarchical framework to interpret the structure, function, change, and stability of
systems by taking into consideration the scale of the analysis and by establishing
relationships among the different scales (Forman 1995).
In applying the concept of landscape ecology we can see that landscapes are
heterogeneous mosaics which combine ecosystems with different degrees of integrity,
which change over time. The biodiversity and the conservation of ecological processes
is not only the result of the amount of area covered by each type of ecosystem, but
 the way in which they are spatially combined and
 the degree of fragmentation and isolation.
Ecological characteristics of the landscape such as connectivity, heterogeneity and
fragmentation, are determining factors of biological wealth and the operational integrity
of ecosystems (Turner 1989).
The loss of habitat and ensuing fragmentation is the main threat affecting biological
diversity in urbanising environments (Saunders and Hobbs 1991). The study of
fragmentation as a process is based on the theoretical foundations, namely the “Island
Biogeography Theory” (Mac Arthur and Wilson 1967), and the Meta-population Theory
(Levins 1969). Island biogeographical studies investigate the influence of isolation
(distance between fragments and/or habitats), and the sizes of the fragments (in terms
the number of species they can support considering the processes of colonisation and
extinction). The meta-population concept describes populations consisting of cellpopulations, and places emphasis on the concept of connectivity on the exchange
between populations which are separated from each other spatially. Fragmentation is
mostly associated with urban and agricultural expansion, and four stages have been
identified in the continuous gradient from unfragmented to completely transformed.
1.
The unfragmented stage (where <10% is destroyed) is referred to as being intact.
2.
The next stage of fragmentation is the variegated stage (where 10 to 40% is
destroyed).
3.
Beyond the variegated stage the process of fragmentation has occurred where
habitat loss disrupts connectivity. This third stage is called fragmented (where 40 to
60% is destroyed).
4.
And the final stage (where > 90% is destroyed) is called relict (Hobbs and
Wilson 1998).
Most often fragmentation is assessed by the reduction of vegetation cover. The
elements of the landscape matrix play an important role in areas that have been
subjected to structural fragmentation. The matrix can increase or decrease the
functionality by acting as a buffer area, while contributing to connectivity by linking
fragments. The functionality of the fragments is also associated with their size, their
shape, and their location with respect to each other. Natural systems that have lost 60%
and more of their habitat start to suffer with respect to conserving biodiversity and
ecosystem integrity (O'Neill et al. 1992).
The main effects of fragmentation is the decrease in habitat area (and the associated
loss of natural cover and biodiversity), the reduction in the size of the fragments (due to
division from larger areas into smaller areas), and the increasing isolation between
fragments (that decreases the quality of habitat for various organisms) (Foreman 1995).
The consequences of fragmentation, for the survival of organisms, are that with
reduction in habitat the size of the population also reduces. The reduction in size of
fragments results in an increased perimeter to area ratio, which increases the
permeability of fragments for extinction to occur. Thus causing risks and increasing the
distance between fragments makes the movement of individuals across the landscape
difficult (Hanski 1999). The geometry of the fragments also influences their ecological
value (Diamond 1975). Highly elongated fragments have less interior habitat and
greater edge effects, and thus reduce the quality of habitat. Edge effects include
physical effects (such as modifications to the microclimate), direct biological effects
(such as a change in species composition), and indirect biological effects (such as
increased disease).
Conservation policies must therefore be directed towards
increasing permeability by maintaining unbroken landscape elements. Consequently the
goal of most conservation biology is to increase the region's connectivity.
Objectives of nature conservation policies have evolved from the protection of flagship
species, unique landscapes, biodiversity, and species habitats, towards the conservation
of ecological processes that operate at landscape levels (Noss 1993). With the
conservation of whole ecosystem processes a range of environmental goods and
services are sustained including species rich communities. Important aspects in the
maintenance of processes are the flows of energy, matter, and information, including
physical factors (e.g. water flows and wind) and/or biotic factors (e.g. animal
movements). It is the strength or attenuation of these flows that dictates the success of
the conservation at the landscape level. Ecological corridors and stepping stones
provide structures that facilitate the maintenance of these ecological flows; and other
landscape concepts such as fragmentation, connectivity, barrier, and/or corridor are
useful for assessing landscape functionality.
Ecological corridors dictate the intensity of matter and energy flows within the local
region, which can result from natural phenomena such as rivers and streams. Although
confusion exists in the definition and effectiveness of corridors (Simberloff et al. 1992),
they are usually divided into structural, functional and legal concepts. The structural
component relates to physical linear elements existing within the landscape, whereas
the functional concepts relate to the dispersal and/or migration - and ensures a level of
protection for the movement of organisms. Further confusion arises between the
connectivity of ecological corridors themselves (as reflected by their continuity or width),
and the connectivity between corridors and adjacent systems (Noss 1993). Corridors do
not necessarily need to be linear, provided they maintain connectivity and eliminate
negative effects of barriers and/or fragmentation. A good example of such a corridor is a
stream-line and strip (Knuffer 1995). Rivers and streams are the most obvious linear
connections within the landscape that can be used to increase connectivity within the
local environment. They not only benefit aquatic animals but they generate refuge or
suitable habitats along the banks for the movement of other organisms. Line corridors
are often the products of human intervention such as hedgerows, but this is not
necessarily always the case - coral reefs are one naturally occurring linear corridor.
Stepping stones and/or broken corridors occur where fragmented habitats are separated
from each other by small distances, which nevertheless still permit the movement of
organisms. The efficiency of stepping stones is also dependent on the width of the
corridor.
Prioritisation of corridors should be according to the following the scheme:
1. The actual or historical presence of species dispersion
2. The actual or historical presence of species migration routes
3. The actual, historical or proposed presence of (mid- or longer-term) movements
of individuals
Ecological corridors should help conservation of the following
1. Bird migration routes
2. River corridors
3. Surface and subterranean water regimes, including the recharge sites for
groundwater replenishment
4. Historical corridors of plants spreading through mountain bridges, along warm
river valleys and across mountain ranges, etc.
The functionality of ecological corridors is influenced by size and shape, and habitat.
They should contribute to maintaining, establishing, or re-establishing natural landscape
connectivity. Corridors are thus seen to be complimentary to the critical functions of
core areas and can be continuous, interrupted, or arranged like stepping stones. They
can contribute to maintaining species numbers, increasing population size, preventing
inbreeding depression, and encouraging the retention of genetic variation within a taxon.
Consequently corridors may lead to increased foraging areas for wide ranging species,
and may provide refuge for those populations that have large distances between their
subpopulations. However, the precise benefits of ecological corridors, with respect to
the maintenance of species and ecosystems, are not known. There is a considerable
shortage of data to define the critical dimensions, distances, degree of connectivity and
the integration of the corridors, into a larger biodiversity network.
It may be necessary to define the criteria for corridors that reflect the projected
functioning of the entire network. For example, different criteria are likely to be required
for a strongly linear ecosystem connection such as a river, as opposed to sites that are
linked like stepping stones which are discontinuations. Consequently it is not easy to
precisely define the criteria for conserving corridors. There are also some potential
disadvantages of corridors such as the spread of predators, the introduction of species
that are highly competitive, and the spread of disease and/or pathogens.
Final the concept of naturalness needs to be briefly reviewed. The Council of Europe,
Pan-European Biological and Landscape Diversity Strategy define naturalness as:
"Traditional man-made landscapes, as well as natural and semi-natural habitats of
European Importance such as coastal zones, marine areas, wetlands, forests, mountain
areas and grasslands are under threat; so are many wild plant and animal species. The
most obvious issues are changes in land use and reduction in area of natural and seminatural habitats, with their resulting fragmentation"
Ecosystems can be classified into
 natural
 almost natural
 semi-natural and
 multi-functional.
In natural and almost natural ecosystems the actual and historical impacts by humans
on the functioning of the ecosystems is nil, or almost nil. Thus in these natural and
almost natural ecosystems, where both the species composition and number (diversity)
have not been influenced by humans, and are not subject to any form of exploitation
(hunting), and/or by direct and indirect ways (modification of watercourses) the
ecosystem functions are intact.
In semi-natural ecosystems the species composition is natural and has been changed
little by humans, but there have been influences on soil and water management
operations - other limited impacts on natural processes could include natural grazing
systems (livestock and or mowing) and limited hunting/fishing (taking over the role of
predators). In multi-functional ecosystems both vegetation, habitat and species
composition have been altered by human use - and soil and water regimes have been
manipulated to increase biomass production.