To Bee or Not to Be: Weeds for Bees

Nimal R. Chandrasena

Keywords:

: Pollinators, pollinator decline, flowers, weeds, ecosystems, honeybees, Apis, Bombus

Abstract:

In addition to the benefits weeds provide to natural enemies of pest insects, weedy taxa are emerging as a critical component that can support pollinators, which are crucial for world crops. Understanding the vital interactions between pollinators, weeds, and crops will enable both the scientific community and the public to appreciate the ecological values of colonizing taxa even more. The species richness of wild bees and other pollinators has declined over the past 50 years, with some species undergoing significant declines and a few going extinct. The causal factors include the excessive use of neonicotinoid pesticides, which directly affect pollinator insects and indirect effects, which include fragmentation of habitat and losses of floral resources due to land clearing and intensive agriculture. Agriculture is recognized as the main driver causing pollinator declines through land-use change, declines in traditional farming practices, intensive farming practices, such as monoculture, tillage and agrochemical use, especially neonicotinoid insecticides, and the excessive use of herbicides for weed control. Agriculture also provides opportunities to support pollinators, through ecologically-friendly farming (Diversified and Conservation Farming Systems) in which habitat can be retained and floral resources for pollinators enhanced. Many countries, especially in Western Europe, the U.K. and the U.S.A., now have programmes dedicated to re-introducing 'green' infrastructure and setting aside field margins and unmanaged areas in agricultural landscapes as Nature-Based Solutions (NSBs) to support pollinators with food resources. The overwhelming evidence from research in the last two decades indicates that colonizing taxa can help bees with rich and diverse food and nectar resources over extended periods. The Convention on Biological Diversity (2018) acknowledges the need to improve knowledge of pollinators and pollination and their role in maintaining ecosystem health and integrity beyond agriculture and food production. Ecological restoration of damaged or modified urban ecosystems can increase the connectivity of pollinator-friendly habitats and support species dispersal and gene flow. These measures can also contribute to climate change mitigation and disaster risk reduction. Weedy taxa, with their abundant flowery resources, have a critical role to play in all of the above.