intervention and the resulting loss of habitat and alteration of biogeochemical
cycles, including those caused by local pollution. In contrast, environmental
harshness explains the high sensitivity of these systems, particularly their difficulties in recovering from disturbances. In fact, this high sensitivity is reinforced by
isolation, due to the limitations imposed on genetic and demographic flux through
dispersal, and by the resulting small populations. Furthermore, steep gradients
contribute to small population size as the habitat area is limited. In contrast, isolation can diminish exposure to deleterious biotic agents—pests, pathogens—at the
landscape scale, although the high heterogeneity promoted by steep gradients may
favour the dispersal of these agents. The spread of other disturbances, such as
wildfires, can also be constrained by the low degree of connectivity, although rough
topography may also enhance the propagation of fire uphill.
The concept of ecological trade-offs provides a useful framework for understanding and designing the allocation of resources devoted to conservation goals,
such as the management of exposure and vulnerability. In organisms, the allocation
of limited resources to different purposes or functions implies a negative relationship between these resources. However, the configuration of this relationship is not
an easy task, first because it is essential to establish a common currency that
accounts for the various functions (Reekie and Bazzaz 1987). A negative correlation between estimators of different functional properties is not in itself a proof of
trade-off unless the mechanisms connecting functional properties can be properly
determined and converted to this common currency. Another key issue is the fact
that these functions are essential for the overall persistence of the system in
question, which in its original ecological sense corresponds to organisms.
Consequently, the product of the estimators of the different functions, after conversion to a common currency (e.g. biomass), should be a constant other than zero,
as a zero value would mean that the system does not exist. One typical case of
ecological trade-off describes the allocation of resources to seed production in
plants (Harper et al. 1970). Assuming a constant amount of resources allocated to
each seed set, seed size and seed number reveal different functions: small seed size
and a large number of seeds would optimise dispersal, while large seed size—in
detriment to number—would favour seedling survival. Obviously, the reality is
much more complex since small seed size may contribute to other functions, such
as minimising genotype losses by predation. Alternatively, a given function usually
determines the involvement of different resources, generating a complex network of
interacting functions and resources that are used to different degrees.
Conservation practice can be considered as analogous to the allocation of limited
resources, and trade-offs would correspond to different management actions. While
natural selection would be the main driver of resource allocation at the species
level, in conservation this role would be performed by environmental managers
involved in decision-making processes. Conservation has an economic component
associated with the allocation of limited funding to different goals (i.e. economic
trade-off). But this funding allocation is intrinsically associated with ecological
properties, which are also subjected to trade-offs.
2 Trade-offs in High Mountain Conservation
41
cycles, including those caused by local pollution. In contrast, environmental
harshness explains the high sensitivity of these systems, particularly their difficulties in recovering from disturbances. In fact, this high sensitivity is reinforced by
isolation, due to the limitations imposed on genetic and demographic flux through
dispersal, and by the resulting small populations. Furthermore, steep gradients
contribute to small population size as the habitat area is limited. In contrast, isolation can diminish exposure to deleterious biotic agents—pests, pathogens—at the
landscape scale, although the high heterogeneity promoted by steep gradients may
favour the dispersal of these agents. The spread of other disturbances, such as
wildfires, can also be constrained by the low degree of connectivity, although rough
topography may also enhance the propagation of fire uphill.
The concept of ecological trade-offs provides a useful framework for understanding and designing the allocation of resources devoted to conservation goals,
such as the management of exposure and vulnerability. In organisms, the allocation
of limited resources to different purposes or functions implies a negative relationship between these resources. However, the configuration of this relationship is not
an easy task, first because it is essential to establish a common currency that
accounts for the various functions (Reekie and Bazzaz 1987). A negative correlation between estimators of different functional properties is not in itself a proof of
trade-off unless the mechanisms connecting functional properties can be properly
determined and converted to this common currency. Another key issue is the fact
that these functions are essential for the overall persistence of the system in
question, which in its original ecological sense corresponds to organisms.
Consequently, the product of the estimators of the different functions, after conversion to a common currency (e.g. biomass), should be a constant other than zero,
as a zero value would mean that the system does not exist. One typical case of
ecological trade-off describes the allocation of resources to seed production in
plants (Harper et al. 1970). Assuming a constant amount of resources allocated to
each seed set, seed size and seed number reveal different functions: small seed size
and a large number of seeds would optimise dispersal, while large seed size—in
detriment to number—would favour seedling survival. Obviously, the reality is
much more complex since small seed size may contribute to other functions, such
as minimising genotype losses by predation. Alternatively, a given function usually
determines the involvement of different resources, generating a complex network of
interacting functions and resources that are used to different degrees.
Conservation practice can be considered as analogous to the allocation of limited
resources, and trade-offs would correspond to different management actions. While
natural selection would be the main driver of resource allocation at the species
level, in conservation this role would be performed by environmental managers
involved in decision-making processes. Conservation has an economic component
associated with the allocation of limited funding to different goals (i.e. economic
trade-off). But this funding allocation is intrinsically associated with ecological
properties, which are also subjected to trade-offs.
2 Trade-offs in High Mountain Conservation
41