Landscape anthropogenic disturbance in the Mediterranean ecosystem: is the current landscape sustainable?



Mediterranean landscape during the last centuries has been subject to
strong anthropogenic disturbances who shifted natural vegetation cover
in a cultural landscape. Most of the natural forest were destroyed in
order to allow cultivation and grazing activities. In the last century,
fast growing conifer plantations were introduced in order to increase
timber production replacing slow growing natural forests. In addition,
after the Second World War most of the grazing areas were changed in
unmanaged mediterranean conifer forest frequently spread by fires. In
the last decades radical socio economic changes lead to a dramatic
abandonment of the cultural landscape. One of the most relevant result
of these human disturbances, and in particular the replacement of
deciduous forests with coniferous forests, has been the increasing in
the number of forest fires, mainly human caused. The presence of
conifers and shrubs, more prone to fire, triggered a feedback mechanism
that makes difficult to return to the stage of potential vegetation
causing huge economic, social and environmental damages. The aim of
this work is to investigate the sustainability of the current landscape.
A future landscape scenario has been simulated considering the natural
succession in absence of human intervention assuming the current fire
regime will be unaltered. To this end, a new model has been defined,
implementing an ecological succession model coupled with a simply Forest
Fire Model. The ecological succession model simulates the vegetation
dynamics using a rule-based approach discrete in space and time. In this
model Plant Functional Types (PFTs) are used to describe the landscape.
Wildfires are randomly ignited on the landscape, and their propagation
is simulated using a stochastic cellular automata model. The results
show that the success of the natural succession toward a potential
vegetation cover is prevented by the frequency of fire spreading. The
actual landscape is then unsustainable because of the high cost of fire
fighting activities. The right path to success consists in development
of suitable land use planning and forest management to mitigate the
consequences of past anthropogenic disturbances.

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