2.1 Natural environmental conditions
A number of natural environmental conditions can be important
for the prospective environmental impacts of pesticides. Some are listed below.
Geology and soil conditions: Information concerning types of
soil in the pesticide treatment area can often be important. The composition and
nature of the soil can be of great importance with regard to the speed of
pesticide degradation and to the speed with which it will be transported through
Hydrological and hydro-geological conditions: Water may carry
pesticides to the surrounding area and be a significant unintended recipient for
pesticides. Large amount of precipitation over short periods of time can carry
pesticides to surrounding areas. Information about expected precipitation during
the spraying period is important. One should also have gained information about
the direction in which the precipitation flows on the ground, and about water
recipients in surrounding areas, such as ground water, brooks, rivers and dams.
The topography is often decisive with regard to what extent and
in what direction wind and water may carry pesticides. Topographical conditions
can for example lead pesticides to nearby brooks and lakes during heavy
Climate: The health conditions of flora and fauna are closely
related to climactic factors such as temperature, humidity and precipitation.
This is also true of pests. Great seasonal variations, as in temperate climates,
reduce the diversity of species, and lead to fewer pests with short life cycles.
Consequently, it is relatively simple to find out at what point the organisms
will be most vulnerable, and thus when to start pest control. In warmer
climates, however, the breeding season for pests is more continuous, and
corresponding measures must be taken to control them. Consequently, pesticides
may be used too frequently. In areas with small climactic variations, constantly
high temperatures and unvarying humidity, pest organisms may have many
generations every year. The reproduction is potentially enormous as long as
there is sufficient nourishment. This can cause serious fungi and insect
problems in many food production and storage areas. A hot climate can also cause
rapid evaporation of pesticides, which means that they can be spread to the
atmosphere and transported across large areas. Wind can transport pesticides
across great distances, either in liquid form or with soil particles. It is
therefore of utmost importance to have information concerning the wind
conditions in the area during periods of spraying or dusting (see chapter 3.1).
Vulnerable ecosystems and rare species can be affected by
pesticides, directly or indirectly. Information about the existence of
vulnerable ecosystems and rare species in the surrounding area is important.
Such information can affect the choice of type and dosage of pesticide, and the
point of time to implement the pesticide