Developing a comprehensive metric to assess the complete impact of food production on biodiversity is impossible. Such a task would require accurately measuring changes in all living species of mammals, birds, reptiles, insects, fungi, bacteria, soil microbes, viruses, etc, so metrics can be developed to assess specific components of biodiversity, such as impacts on birds or aquatic life. While these targeted assessments provide one perspective, they fail to account for important but tangential changes. An example is the change in wetland areas, where overall wetland areas may be reduced due to farmers draining these lands, and an assessment could conclude this was harmful to bird biodiversity. However, these types of analysis fail to consider the additional amount of food that is now able to be produced and the benefits that come from the increased food production. There is not likely a benefit-cost analysis’ taking place for each farmers decision to drain a wetland on their land. Alternatively, many farmers have cleared trees, shrubs and bushes from their farmland. Some will view this as reducing the habitat for birds and other wildlife, however, these views fail to consider the reduced amount of GHG emissions from farm equipment that no longer has to take extra time to constantly travel around small areas of trees. An additional trade-off would be whether a small number of trees sequester more carbon during a year, than the thousands of crop plants that would be growing in the same space.
Changes in land use impact biodiversity. If land is deforested to be used for livestock or crop production, biodiversity will change. Similarly, if land once used for crop or livestock production is purchased to be part of a protected biodiverse area, changes will again occur. The challenges for assessing impacts on biodiversity from land use change are illustrated in this example. Suppose an area of land is clear of trees, containment basins for water will be created and the land is used for livestock production. This change could negatively impact populations of larger mammals such as moose, elk and deer. This change could positively impact changes in the number of wetland birds using the created water reservoir or grassland mammals such as antelope. Trying to create a metric that would meaningfully compare potential declines in large mammal populations to potential increases in aquatic bird populations is extremely difficult requiring many assumptions, that may, or may not, have sufficient data to verify the assumption. Any outcome would be a subjective opinion of the individual undertaking the evaluation, highlighting the challenge of obtaining truly objective assessments.
Some ecologists are beginning to advocate for invasive species to be considered part of biodiversity and allowed to remain, even though they may be causing significant economic and environmental harms and potentially reduce the production of food. This highlights the gaps in agreement as to what should be considered to be part of a specific biodiversity area and how to robustly assess changes that benefit or harm biodiversity.
