Agriculture Reference
In-Depth Information
(Flowerdew 1997). Wickramasinghe
et
al
. (2003) investigated bat activity and species richness
in a paired (organic/conventional) farm. Total bat activity was significantly greater on organic
farms than on conventional farms, while no significant difference in species richness was
found between the farm types. Responsible factors for the greater activity levels appeared to be
better water quality and greater prey availability.
Comparatively few data are available on the effects of organic farming on other wild animal
groups, particularly in regard to pollinators. This could be an important research theme. Apart
from wild bees and other insects, bats are the principal pollinators of fruit trees and major
staple food crops, including potato, cassava, yams, sweet potato, taro, beans, coffee and
coconut. Declines in populations of pollinators now threaten both the yields of major food
crops and the survival of wild plant species (McNeely and Scheer 2001). Many vertebrate polli-
nator species are threatened in Australia, Colombia, Ecuador, Indonesia, Madagascar, Mexico,
Papua New Guinea, Peru and the USA. The main reasons include: loss of nesting and roosting
sites, habitat fragmentation by excessive exposure of nectar plants to herbicides and pollina-
tors to pesticides, overhunting, disruption of nectar corridors required by migratory pollina-
tors, and competition by invasive species (Nabhan 1998).
Habitat diersity
Semi-natural areas are extremely valuable habitats in the agricultural landscape with respect
to the conservation of threatened species. They are also of great functional importance for
nutrient cycling (e.g. meadows retaining nutrients and thereby preventing leaching) and proc-
esses of succession (e.g. colonisation) (Tybirk
et
al
. 2004).
In Denmark, there are four major pressures which affect semi-natural habitats such as per-
manent grasslands and meadows: changes in hydrology, fragmentation, eutrophication, lack
of management and consequently, succession into shrub and forest (Ellemann
et
al
. 2001).
Tybirk
et
al
. (2004) argue that organic farming may affect these biotopes in the same manner
as conventional farming except for the absence of chemical fertilisers and pesticides. While
pesticides are rarely used on semi-natural areas in general, organic nutrients may be applied by
organic farmers at (almost) the same levels as in conventional farming systems. Attention
should therefore be given to developing organic farming practices that support the characteris-
tic balance of functional groups of organisms, and that ensure a proper functioning of the
relevant processes and functions (Stolton
et
al
. 2000). An example is the maintaining of unfer-
tilised buffer strips along uncultivated biotopes (Tybirk
et
al
. 2004).
Overall, there is little information available to compare habitat diversity in organic and
conventional farming systems. Stockdale
et
al
. (2001) and Alföldi
et
al
. (2002) indicate that
semi-natural habitats are intrinsic in organic regimes where their management is central to the
philosophy. Organic farming does indeed tend to have a positive impact on habitat diversity,
presumably for the reasons that have already been given. But the correlation is not very strong,
since habitat diversity depends highly on given/historic landscape structures and site-specific
aspects too (Stolze
et
al
. 2000, Shepherd
et
al
. 2003, Reiter and Krug 2003).
Diversity and density of habitats in the agricultural landscape may inf luence the produc-
tion system, but the overall effects are extremely difficult to determine. There is a great need to
intensify research of these interactions and to develop reliable indicators of a supposed func-
tional integrity and both the positive and negative interactions between cultivated and uncul-
tivated areas in organic farming systems (Tybrik
et
al
. 2004).
Landscape
Landscapes are territorial or spatial units produced through the interaction between human
societies and cultures with the natural environment (Wascher 2000). They are viewed as
