A. Habitat fragmentation is the process of habitat loss in which larger habitats get divided into many small and fragmented habitats. This destroys the natural home of many species and affect biodiversity.
B. Biological magnification is the accumulation and increase in concentration of a toxic chemical, at successive trophic levels.
C. Contour ploughing is the ploughing of land according to its contour or slope and this helps in preventing soil erosion.
D. Introduction of non-native species can become a threat to biodiversity as they compete with the native species for resources. For example, Water hyacinth which multiplies at a very high rate.
E. Desertification of land has lead to destruction of soil microflora and natural habitat of many species of plants and animals.
Hence, contour ploughing won't affect biodiversity.
So, the correct answer is 'Contour ploughing'.