Everybody talks about the long-term decline in farmland bird populations because this group has been effectively monitored for the longest period. But there is a growing list of other important farmland taxa that are being monitored including plants and butterflies. Defra released the 2012 report on these Biodiversity Indicators yesterday.
Since 1990, the results indicate a continued shallow decline in farmland birds and a decline in butterfly numbers. On the plus side, bat numbers seem to be picking up over the last 10 years after a sharp decline between the late 70’s and the mid-90’s. It does seem to be a reoccurring theme, that significant declines in wildlife abundance happened in the 1970’s and 1980’s, with relatively minor changes since then. However, we are confident that a recovery of biodiversity on farmland is realistic if the most can be made of opportunities through agri-environment schemes. We now have about 70% of farmland in England in agri-environment, and Defra are trying to make Entry Level Stewardship more effective at benefiting the environment.
The results for arable plants seem odd to me. They report an increase in plant species richness in arable fields between 1990 and 1998, and again between 1998 and 2007. Arable plants are one of the most threatened plant groups in the UK, making them a high priority for Plantlife . This is supported by studies on the diets of seed-eating birds such as the turtle dove and linnet, which are increasingly dependent on the seeds of very few common species. The loss of seed food on farmland generally has been one of the biggest drivers of farmland bird declines. Plants that do seem to be doing well on modern arable farms are the highly-competitive, nitrogen-demanding weeds, such as blackgrass and cleavers.
There are few more rewarding achievements for wildlife on arable farmland than properly sited and managed cultivated margins for arable plants. A huge array of flowering plants can emerge after decades of sitting in the seed bank unseen.