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close this bookInitial Environmental Assessment: Plant Protection - Series no 13 (NORAD, 1995)
close this folderPart I: General account
close this folder2 The environment affected by the project
View the document2.1 Natural environmental conditions
View the document2.2 Man-made environmental conditions

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 the soil.

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 rainfall.

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 treatment.