The influence of disturbance
Disturbance
- introduces heterogeneity into
the landscape. It brings about changes in ecosystem balance, which in
turn alters the flows of elements across the landscape.
- varies in magnitude, intensity,
severity, frequency, predictability, and spatial association. Human
disturbance can resemble natural disturbance but it varies from natural
disturbance in terms of severity, timing and magnitude.
- can alter the scale of spatial
pattern and process. Human and natural processes tend to operate on
different scales, resulting in different disturbance patterns.
- can be caused through the
absence of an event as well as events taking place eg - absence of fire
in Eucalypt forests in Australia that require fire for regeneration.
Natural land cover patterns are the result of complex
interactions between climate, terrain, soil, water availability and biota.
Humans alter land cover patterns through urbanisation, agriculture and
forestry. They remove part of the natural vegetation and replace it with
managed systems of different structure.
The result of these disturbances is a landscape that
is a mix of natural and human managed patches of different sizes and shapes
(Krummel
et al., 1987).
The most sensitive indicator of disturbance or landscape
change is the local biota, so it is usually used as a way of quantifying
change.
Some species are dependent on natural disturbance taking
place so their richness and abundance is a function of the form and history
of disturbance (like seagulls, and a number of weed species).
Susceptibility to disturbance is also often affected
as a result of changed structure and composition of the landscape.
