sustainable use of biological diversity.pdf - India Environment Portal

Sustainable use of biological diversity in socio-ecological production landscapes
© Image Bank. Instituto de Tecnologias Educativas.
figure 2. dehesa landscape with holm oaks.
1.6 Threats
A number of factors are causing decay in tree density,
coverage and functions in the last decades. One
in particular has a particular environmental character,
the disease termed seca, or sudden die-off of the
trees, that has its roots in the stress caused by the
lengthening of the dry season and the opportunistic
invasion of a fungus.
Other important factors have an anthropogenic
and historical nature. In periods of severe starvation,
particularly in the 1950s, trees were cut and land was
put into cultivation. Later on, the crisis of the African
swine fever caused a dramatic decline of the black
Iberian pig livestock –not completely recovered thus
far- and the disruption of the pastoral function of
the dehesa, which ultimately led to transform it to
arable land. The introduction of non-native swine
breeds, with a higher productivity, to supply an increasing
demand for meat led to a steep decline of
the black pig livestock. Also, the partial substitution
of cattle for sheep, due to changing market demands,
is increasing grazing pressure in the number of units
and duration. The result is a landscape that does not
already hold mixed species and multiple breeds but a
single dominant species, particularly cattle.
And, more importantly, the focus of the European
Common Agricultural Policy on productivity and
single crops, and the unawareness of the systemic
operation of this agrosilvopastoral economy led to
a poor access to financial resources, and to a loss
of ability to perform successfully in an agricultural
market dominated by competitiveness and not by
sustainability.
1.7 Local economies
The dehesa historically (at least during the Middle
Ages) exhibits a successful integration of a ruralbased
economy with nature conservation and biodiversity
preservation. Yet multifaceted, the dehesa
essentially aims at extensive livestock production,
so that other activities turn out to be subsidiary or
complementary. Pastoral husbandry is based both
in browsing and grazing. Animals forage by themselves
natural pastures and low vegetation, completing
shrub control, or feed on leaves, soft shoots, and
fruits (oak acorn) such. Thus, shortage of fresh fodder
is supplemented with browsing and grazing immature
cereal crops. Every two to five years cropping
is carried out to both provide for forage and control
shrub species invading the herbaceous layer. Yield is
in the range of 1200 to 1800 kilograms per hectare
per year, depending on tree coverage.
Silviculture is based on the production of firewood,
cork harvesting and the utilization of oak acorn for
swine foraging, with yields of 200-400 kilograms
per hectare per year, a process that runs from October
until January and known as montanera. Branch
pruning occurs every 10-20 years, and debarking
happens every 9-12 years.
Hunting evolved from a deep-rooted complementary
resource into a key economic activity detached
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