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T.J.B. Boyle
rather than as the goal itself. Lande (1988) also stressed the improtance
of considering processes, in designing conservation strategies. In reviewing
recovery plans for two endangered .bird species in America, Lande postulated that strategies based on demographic processes would have a
far greater chance of success than the existing strategies based on the
population genetics of the two species.
Biodiversity is arranged in distinct spatial patterns at all levels. The
distribution of genetic diversity is often found to be non-random (e.g. ,
Linhart, Mitton, Stwrgeon et al., 1981). Species distribution is also usually
associated with discrete patches of habitat. Although on a broad scale
the distribution of habitat is clearly realted to environmental variables,
the significance of small-scale patterns and the nonrandom distribution
of genetic diversity is not well understood (Lovejoy, 1988). Human
manipulations typically tend to simplify or eliminate spatial patterns.
Natural mixed forests are often replaced by plantations of a single, or a
few, species. The genetic diversity of these plantations may be random,
overdispersed, highly structured or, in the extreme case of monoclonal
plantations, absent. The risks associated with a reduction in biodiversity
are well known from past experience and ecological theory, and policy
guidelines are usually devised to address this issue, but management
guidelines governing pattern and distribution are generally more con -
cerned with convenience than with any ecological principles.
Increasingly, theories derived in fields of science such as mechanics and
engineering are being modified and adapted for use in ecology. One such
theory governing the movement of particles through a matrix, " percolation
theory" (Stauffer, 1985), predicts that if there exists a critical set of sites
through which energy or material flows (the " backbone" ) , the loss of
other sites will have no significant effect, whereas the loss of a backbone
site would have far greater consequences (Gardner & Turner, 1991). This
concept, which is of obvious relevance to maintenance of ecosystem
processes, infers that, the identification of " keystone habitat patches"
may be more significant that the classification of species as being keystone
species. Experimental or empirical evidence for the validity of such a
concept has not yet been obtained.
Future Initiatives
In the past few years there have been a large number of international
policy initiatives, most of them with the involvement of foresters , that
have conducted valuable analyses of actions required to manage and
conserve biodiversity. Such initiatives include the report of the World
Commission on Environment and Development (the " Bru ntland Commission"), published in 1987, various products of the 1992 United Nations
Conference on the Environment and Development (UNCED), the
T.J.B. Boyle
rather than as the goal itself. Lande (1988) also stressed the improtance
of considering processes, in designing conservation strategies. In reviewing
recovery plans for two endangered .bird species in America, Lande postulated that strategies based on demographic processes would have a
far greater chance of success than the existing strategies based on the
population genetics of the two species.
Biodiversity is arranged in distinct spatial patterns at all levels. The
distribution of genetic diversity is often found to be non-random (e.g. ,
Linhart, Mitton, Stwrgeon et al., 1981). Species distribution is also usually
associated with discrete patches of habitat. Although on a broad scale
the distribution of habitat is clearly realted to environmental variables,
the significance of small-scale patterns and the nonrandom distribution
of genetic diversity is not well understood (Lovejoy, 1988). Human
manipulations typically tend to simplify or eliminate spatial patterns.
Natural mixed forests are often replaced by plantations of a single, or a
few, species. The genetic diversity of these plantations may be random,
overdispersed, highly structured or, in the extreme case of monoclonal
plantations, absent. The risks associated with a reduction in biodiversity
are well known from past experience and ecological theory, and policy
guidelines are usually devised to address this issue, but management
guidelines governing pattern and distribution are generally more con -
cerned with convenience than with any ecological principles.
Increasingly, theories derived in fields of science such as mechanics and
engineering are being modified and adapted for use in ecology. One such
theory governing the movement of particles through a matrix, " percolation
theory" (Stauffer, 1985), predicts that if there exists a critical set of sites
through which energy or material flows (the " backbone" ) , the loss of
other sites will have no significant effect, whereas the loss of a backbone
site would have far greater consequences (Gardner & Turner, 1991). This
concept, which is of obvious relevance to maintenance of ecosystem
processes, infers that, the identification of " keystone habitat patches"
may be more significant that the classification of species as being keystone
species. Experimental or empirical evidence for the validity of such a
concept has not yet been obtained.
Future Initiatives
In the past few years there have been a large number of international
policy initiatives, most of them with the involvement of foresters , that
have conducted valuable analyses of actions required to manage and
conserve biodiversity. Such initiatives include the report of the World
Commission on Environment and Development (the " Bru ntland Commission"), published in 1987, various products of the 1992 United Nations
Conference on the Environment and Development (UNCED), the