Dividing species and their impact into “useful” and “harmful” is an undue simplification, the scientists say. In agriculture in particular, one insect species or microorganism may have an overall benefit for certain types of cultivation and be detrimental to others, they point out.

Wherever a plant protection agent is applied, resistant organisms can completely crowd out the vulnerable ones. Even if it was then theoretically possible to exterminate certain pathogens or insect pests on a global scale, this could entail considerable health and environmental costs, the researchers warn.

Unproblematic extent exceeded by far at regional level

However, the alarm sounded by the resistance project appears to have come too late. Horizontal gene transfer and global transport networks have resulted in a massive spread of resistant organisms. The results of the study are straightforward. Even if the general situation regarding resistance to herbicides and insecticides has not yet been fully clarified owing to insufficient data, the extent of resistance spread lies outside the harmless zone, both regionally and globally.