Environmental Engineering Reference
In-Depth Information
Sustainability is partly a difficult concept because hunting systems are
dynamic
—they change over time, rather than being at a single equilibrium position.
This is because there is variability in the system—the weather, chance events like
accidents, political changes and so on. This variability knocks the system out of
equilibrium, and acts at different scales in time and space. Table 1.1 gives some
examples of the kinds of processes acting on sustainability at different scales. Some
of these involve predictable and non-trending variation (e.g. seasonal food avail-
ability), some are not so predictable (short-term weather variation). Some involve
sudden shifts in the system (e.g. wars), others relatively deterministic trends (e.g.
human population growth). Sometimes, events do not have the expected effects on
sustainability. For example, the Critically Endangered Virunga mountain gorilla
population actually increased during the 1990s, a period of unparalleled civil
unrest. One of the reasons for this is that the conservation programme put in place
in peacetime was robust enough, and had built enough local support, to continue
even when the rest of civil society was in disarray (Kalpers
et al
. 2003).
Given the range of scales at which these effects act, and their ubiquity, it is clear
that assuming that human-environmental systems are at equilibrium is often
Table 1.1
Examples of social, financial and biological events that can affect
sustainability of exploitation at different time-scales and spatial scales.
Few days
Few months
Few years
Many years
Few km
2
Cold/wet
Food
Village head
Change of
weather.
availability
changes.
culture and
Hunter
for prey.
New job
social
health.
Alternative
opportunities.
institutions.
Village
activities
Human and
Local prey
festivals.
for hunters.
prey population
adaptations.
size changes.
Few hundred
Major
Fires,
Food
Evolutionary
km
2
regime
Droughts,
preferences
change.
change.
Harsh
in city change.
winters,
Changes in
Floods,
national
government.
Continental/
Commodity
El Nino
Wars.
Climate
Global
price
effects,
Environmental
change.
changes.
e.g. coral
treaties.
Internet
bleaching.
information
Reactions to
transfer.
commodity
prices.
