It is widely believed among ecologists that humans have triggered what is now the early stages of the Sixth Mass Extinction event, much of it related to landscape simplification (cf. Kolbert, 2014; Dasgupta et al., 2019). With 11% of the earth's land in crops and another 30% grazed, agriculture is a major force of biodiversity decline across all classifications of organisms (Newbold et al., 2015). Essentially, agriculture is a major force globally contributing to the surpassing of planetary boundaries (cf. Loken et al. (2020).
Agriculture has also been a force reducing Canadian biodiversity. This has happened as a result of numerous activities:
- The destruction of native habitat when farmland is created. For example, approximately 93% of Prairie ecozones are in agriculture and only 1% of the tall grass prairie, 19% of the mixed grass prairie and 16% of aspen parkland remain (McRae, 2000). One of the likely impacts is that over half of bird species in the Breeding Bird Survey are in decline on the prairies, particularly grassland species (Downes and Collins, 2003).
- The destruction of corridors and habitat adjacent to farmed fields. Agriculture is a major cause of habitat fragmentation, with disconnected parcels of woodlots across the landscape, and the elimination of field borders that serve as corridors for wildlife movement.
- Pollution from agricultural practices (e.g., synthetic pesticides, synthetic fertilizers, soil and manure runoff associated with poor management) disrupts terrestrial and aquatic ecosystems and changes wildlife populations. Pesticides kill many non-target organisms, especially birds and insects. The cost of pesticide damage to all natural capital in the U.S. has been estimated at $3.70 / kg of active ingredient applied (Pretty et al., 2000).
- Simplification of agroecosystems (e.g., very limited crop rotations that result in vast acreages in only 2 or 3 crops, and poor range management) removes habitat and food sources.
- Weed management practices (excessive tillage, herbicides, herbicide - tolerant (GE) crops) that eliminate food sources and disturb ground habitats
- Poor management of wetlands, streams and riparian zones on farm properties, including excessive access to these areas by grazing animals.
- Introduction of exotic species (plants, pests). Agriculture is a major source of new species introduction to natural ecosystems.