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; Maxwell et al., 2016; 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 et al., 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.
AAFC has been using a somewhat limited wildlife habitat capacity on farmland measure in its agri-environmental indicator report series, based on Census of Agriculture data from 1986 to 2011. Although there has been stability on much farmland over this time (though starting from a suboptimal state), there were significant declines in capacity on 14% of farmland from 1996, leading to an overall decline for the period and overall Poor status. Problems were most related to increases in cropland intensity and losses in hay and grasslands.
In a 2020 report, WWF Canada identified numerous areas of the country with significant agricultural activity as high priorities for action to reverse biodiversity and wildlife loss, including the Okanagan, BC, the Prairie grasslands, Southern Ontario and Quebec, and the St. John River Valley watershed of NB. Most of these regions have very low to no protections, largely related to patterns of private land ownership and management. In some regions of the country with significant agricultural active, detailed assessments have been conducted of biodiversity decline (cf. ESTR Secretariat, 2016). Ray et al. (2021) highlight that 20% of Canada's 30,000 species are imperilled to some degree, with particularly significant losses associated with wetland and grasslands, often a result of agricultural landscape manipulation.