中欧社会论坛 - China Europa ForumThe Progress of Comparative Research on the Impact of Organic Agriculture and Conventional Agriculture on Agricultural Biodiversity
Authors: Wang Changyong
Date: février 2007
Published by Journal of Ecology and Rural Environment
In the recent 20 years, many scientists from Europe, North America and Oceania have conducted studies on the impact of organic agriculture on agricultural biodiversity, using the modern conventional agricultural production system as a comparison.
They have also obtained a number of important scientific findings. Nevertheless, China’s research in this field is still almost negligible. In order to promote China’s scientific interest and research in this field, this paper has reviews the research progress on the impact of organic agriculture on various agricultural biological species.
1. Organic agriculture helps the growth of farmland weeds
Compared to conventional agricultural land, the number of species of farmland weeds in organic agricultural land is 23 times that of conventional agricultural land. Organic agriculture better supports the growth of rare or endangered farmland weed species. There are several reasons for this: First, extensive use of herbicides can lead to a decrease in the richness of agricultural weed species; next, extensive use of nitrogen fertiliser can lead to decreased agricultural weed species richness and changes in weed communities; furthermore, nitrogen fertilisers cause crop plants to grow more densely, thereby restricting the weeds from absorbing sunlight; and finally, surrounding farmland landscape will also affect the richness of weed species. Organic weed species diversity is significantly higher than that in simple landscapes, but when the surrounding landscape becomes complex, it is comparable to conventional agriculture.
2. The richness and abundance of arthropod species (invertebrate animals, like insects) in organic farmlands are higher than in conventional farmlands.
Organic agriculture better supports the richness and abundance of arthropod species but the reaction of different species to different agricultural production systems are also significant different. There are four main reasons why the diversity of arthropod species in organic farmlands are higher: First, crop species, quantity and coverage in organic farmlands are relatively higher and can serve as a suitable habitat for arthropods to rest and feed; second, there are host plants in organic farmlands which are suitable for certain arthropod species; third, the large number of some non-herbivorous arthropods is related to the use of manure fertiliser in organic farmlands; and fourth, the non-use of chemical fertilisers and pesticides can provide good living conditions for arthropods.
3. The impact of other organisms
For the same reason, the abundance of earthworms and richness in species in organic farmlands exceed that of conventional farmlands; at the same time, in comparison with conventional farmlands, the abundance of nematodes, or roundworms, in organic farmlands are increasing. Furthermore, the management practices and habitat characteristics of organic agriculture allows the fields and their surroundings to have more species and numbers of invertebrates and plants, hence resulting in an average richness and abundance of bird species which are 2.0 times and 2.6 times respectively of that of conventional farmlands. However, there is no significant difference in the amount of bacteria and fungi in organic farmlands and conventional farmlands.
It is generally believed that organic agriculture contributes to the maintenance of biological diversity in agricultural ecosystems or increases the impact of various factors including study sites, climatic conditions, type of field crops, biological species as well as some specific field management practices. The extent of impact which organic agriculture has on various biological species differ greatly and are closely related to the above-mentioned factors. Therefore, there is a need to conduct a comparative research on the organic agricultural production systems of different countries to study the impact of organic agriculture and conventional agriculture on agricultural biodiversity, in order to verify the claim that organic agriculture supports biodiversity as well as to support it with various scientific evidence.