Pesticides are a major factor affecting biological diversity, along with habitat loss and climate change. They can have toxic effects in the short term in directly exposed organisms, or long-term effects by causing changes in habitat and the food chain.
What is biodiversity?
Charles Darwin and Alfred Wallace were among the first scientists to recognise the importance of biodiversity for ecosystems. They suggested that a diverse mixture of crop plants ought to be more productive than a monoculture (Darwin & Wallace 1858). Though there are exceptions, recent studies confirm the idea that an intact, diverse community generally performs better than one which has lost species (Chapin et al 2002). Ecosystem stability (resilience to disturbance) seems to arise from groups of connected species being able to interact in more varied positive and complimentary ways (Tilman 2002). Biological diversity manifests itself at different levels. It includes the diversity of ecosystems, species, populations, and individuals. In an ecosystem, interdependent populations of various species deliver ‘services’ such as the supply of food and soil resources, or the retention and cycling of nutrients, water and energy. Although it seems that the average species loss can affect the functioning of a wide variety of organisms and ecosystems, the magnitude of effect depends on which particular species is becoming extinct (Cardinale et al 2006).
- Communities of different animal and plant species perform vital functions within ecosystems. In general, communities which have higher diversity tend to be more stable.