Report from the Sub-comittee on the environment and health

Impact on <strong>the</strong> field's
arthropods
192
On <strong>the</strong> basis of studies of <strong>the</strong> effect of pesticides on springtails,
earthworms, five species of weed and nine species of bird and on algae
and daphnia in <strong>the</strong> aquatic environment, models have been constructed
for calculating <strong>the</strong> consequences of a total or partial phase-out of
pesticides for <strong>the</strong> respective organisms. The results of <strong>the</strong> model
calculations must be regarded as a best idea of <strong>the</strong> consequences on <strong>the</strong>
basis of <strong>the</strong> underlying studies and assumptions, but not as an exact
expression of <strong>the</strong> consequences for <strong>the</strong> organisms in question. In this
connection, it must be stressed that <strong>the</strong> model calculations must not be
taken, ei<strong>the</strong>r, as an expression of <strong>the</strong> consequences for all o<strong>the</strong>r
organisms in <strong>the</strong> terrestrial and aquatic environments.
10.3.1 The fauna in cultivated and uncultivated terrestrial
ecosystems
Up through <strong>the</strong> last century, farming in Denmark has become
increasingly intensive. Farm units have become larger and drainage more
intensive, and <strong>the</strong>re has been a high degree of specialisation. The higher
degree of specialisation has resulted in monoculture of cereals and
increased use of fertiliser and pesticides. In step with <strong>the</strong> intensification
of farming, <strong>the</strong> cultivated land's flora and fauna have also changed. Many
plants and animals that used to be common in <strong>the</strong> midfield or in hedges
and small biotopes have decreased in number or disappeared altoge<strong>the</strong>r.
In this connection, <strong>the</strong> increased use of pesticides is presumed to play a
critical role with respect both to <strong>the</strong> reduced biological diversity in arable
land and to <strong>the</strong> decrease observed in <strong>the</strong> populations of some animals and
plants living in <strong>the</strong> agro-ecosystem.
The crop rotation is an important factor for <strong>the</strong> conditions of life in <strong>the</strong>
field, since <strong>the</strong> choice of crop also partially determines <strong>the</strong> use of
pesticides, soil treatment and fertilisation, and <strong>the</strong> timing of <strong>the</strong> various
operations. It is estimated that <strong>the</strong> restrictions on <strong>the</strong> use of pesticides in
<strong>the</strong> 0-scenario would mean a changed crop rotation. Changes in <strong>the</strong> crop
rotation would affect some of those fauna that are not affected by <strong>the</strong> use
of pesticides. Pesticides have a considerable impact on arthropods. They
have less effect on springtails and earthworms, but changes in <strong>the</strong> crop
rotation could have a big impact on <strong>the</strong>ir populations. For farmland birds,
analyses have been carried out of <strong>the</strong> consequences of both changes in
pesticide use and crop rotation.
The lower fauna are affected both directly by treatment with insecticides
and indirectly through <strong>the</strong> removal of plants and microorganisms as food
resources through <strong>the</strong> use of herbicides and fungicides. The effect of <strong>the</strong>
different types of pesticide is partially specific and proportional to <strong>the</strong>
frequency of treatment with fungicides, herbicides and insecticides (see
figure 10.3). In comparisons of <strong>the</strong> scenarios, <strong>the</strong> treatment frequency
index is <strong>the</strong>refore an indicator of <strong>the</strong> undesirable side-effects of pesticide
use on individuals, species and communities of flora and fauna, assuming
that <strong>the</strong> treatment frequency index is an expression of <strong>the</strong> size of <strong>the</strong>
treated area. If treatment with herbicides were omitted, <strong>the</strong> insect fauna
above <strong>the</strong> ground could be expected to increase by a factor of 2-7,
measured as individuals, and by a factor of 1.5, measured as number of
species per sample. If treatment with fungicides were omitted, <strong>the</strong>
fungivorous insect fauna would increase for a time by a factor of 1-2.5. If