Landscapes Forest and Global Change - ESA - Escola Superior ...

J.M. Rey Benayas 2010. Restoration of biodiversity and ecosystem services in cropland
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Convention for Biological Diversity and the sustained global biodiversity crisis (Sutherland et al.
2009). The scientific community must search for ecological restoration protocols and models
that allow a synergy between the exploitation of ecosystems and nature conservation, which will
in turn improve the sustainability of systems for the exploitation of natural resources.
2. The agriculture and conservation paradox
Few human activities are as paradoxical as agriculture in terms of their role for nature
conservation. On one side, agricultural activities are the main cause of deforestation worldwide,
which has occurred at an estimated global rate of 130,000 km 2 per year over the last five years
(FAO 2006). Traditional agriculture allowed remnants of natural vegetation to remain on steep
hillsides, valleys, rocky outcrops, shallow soils, saline and infertile areas, property boundaries
and track edges. In recent history farming practices in many areas have become intensified, and
increasing amounts of water, fuel, fertilizers, pesticides, and herbicides are used worldwide to
increase food and fiber production. E.g., global area equipped for irrigation expanded by 0.3%
to 280 million ha between 2004 and 2005, and at present irrigated area accounts for ca. 20% of
cultivated land. Intensification of land use has brought remnant areas of natural vegetation into
mainstream agriculture and many such areas have been lost or severely degraded. The
conversion of natural ecosystems to human land-uses seems to have ensured our food supplies
at a global scale. However, food security has damaged the regulation function of ecosystems.
Whereas the provision of environmental services such as crops and livestock production have
increased, hydrological and climate regulation, soil retention, and greenhouse gas mitigation
have decreased as a consequence of overall degradation of ecosystem services by 60% in the
last 50 years (Millenium Ecosystem Assessment 2005).
However, deforested habitats as a result of agricultural activities have been often granted a
relevant role in nature conservation (Kleijn et al. 2006). Thus, of the seven main categories of
terrestrial habitats in the EU Habitats Directive, four include agricultural and livestock land uses
(pastures, scrub, “dehesas” and “montados”, etc.). Several species, some of them endangered,
especially birds, depend on agrarian systems (http://www.birdlife.org/). Agricultural
intensification can have a negative impact on these values, but so can agricultural
abandonment and, particularly, afforestation of former cropland. It seems that
agriculture, woodland, and biological conservation are in a permanent and irreconcilable
conflict, the agriculture and conservation paradox. This creates a dilemma in woodland
restoration projects, which can only be resolved by considering the relative values
associated with woodland vs. agricultural ecosystems. Can we solve this dilemma
3. Contrasting approaches for vegetation restoration in abandoned cropland
Abandoned agricultural land, i.e. cropland and pastures where extensive livestock farming has
been removed, can be subject of secondary succession or passive vegetation restoration.
Worldwide, land abandonment and passive restoration have revegetated a greater surface area
and at a smaller cost than active restoration (45,000 Km 2 /year vs. 28,000 Km 2 /year, respectively,
in 2000-2005; in Europe, agricultural land area have declined by ca. 13% between 1961 and
2000). Passive restoration is cheap and genuine since all ecological filters are at play, It is
generally fast in productive environments, but usually slow in low productivity environments
such as the Mediterranean. This is because woody vegetation establishment is limited, since
conditions in bare areas are different to those of places where trees and shrubs regenerate
naturally (Rey Benayas et al. 2005). A key bottle-neck that hinders revegetation is lack of
propagules due to absence of mother trees and shrubs due to complete destruction of the original
vegetation.
Forest Landscapes and Global Change-New Frontiers in Management, Conservation and Restoration. Proceedings of the IUFRO Landscape Ecology
Working Group International Conference, September 21-27, 2010, Bragança, Portugal. J.C. Azevedo, M. Feliciano, J. Castro & M.A. Pinto (eds.)
2010, Instituto Politécnico de Bragança, Bragança, Portugal.