Habitat Fragmentation

Habitat fragmentation and loss of natural habitats are major threats to many bee
populations. Much of North America’s natural habitats have been transformed into highways, houses, strip malls, office complexes, and industrial parks. Urbanization not only directly removes bee habitat but it also isolates and fragments the land in which bees are trying to travel across[1]. Fragmentation can also reduce gene flow between populations, thus decreasing genetic diversity for certain bee species. By being isolated, it is harder for bees to find mates, have enough nesting sites and eat enough food within a limited area.

Bees that experience habitat loss are suffering from nutritional stress as it is more difficult for them to locate valuable food sources. In the United States, states with the largest areas of open land compared to developed land had a significantly higher honey yield on a per colony basis because of more foraging resources in the open land. Scarcity of pollen and nectar can reduce adult survival rates as well as brood development rates, which could quickly diminish a population[2].

Agricultural intensification has been proven to reduce the biodiversity and abundance of native bees in North America, such that pollination services are below the necessary threshold for producing marketable products[3]. Diversity of bee populations is important because of year to year variation in plant community composition. For example, some bee species that are unimportant one year are beneficial in the next year because of the availability of crops and what bees are best suited to pollinate.

There is growing evidence suggesting that in countries where bees are declining, so are the plants that are reliant on these bees for their reproduction[4]. For example, in Britain and the Netherlands, where there has been extensive anthropogenic environmental degradation, specialist bees (i.e. bees with longer tongues, strict dietary and habitat needs) have been declining, and so have their obligately outcrossing plants reliant on insect pollinators. This stresses the importance of plants’ dependence on vital pollinators and therefore the dependence of humans on bees.

Farmers have imported the European honey bees (Apis mellifera) for centuries because of their pollination services, but these bees have also been declining due to diseases, pesticides etc. Therefore, this means that it is necessary for us to conserve our native bee populations if we want crop pollination to continue at the rates necessary to sustain our growing population. This means conserving native bee habitats and minimizing the amount of environmental degradation in locations where these bees thrive.

How can you make a home for native bees?

Most Canadian native bumblebees live in small holes in the ground[5]. A modest open space, untilled, will provide lots of homes for many kinds of native bees. Bees also often live in fallen trees, branches, rock piles, and other debris. So, the next time you try to “tidy’ up your lawn, you can reserve some untidy spots for bee homes.

[1]Cane, J. H. and V. J. Tepedino. 2001. Causes and extent of declines among native North American invertebrate pollinators: detection, evidence, and consequences. Conservation Ecology 5: 1.

[2] Naug, D. 2009. Nutritional stress due to habitat loss may explain recent honeybee colony collapses. Biological Conservation 142: 2369-2372.

[3] Kremen, C., N. M. Williams and R. W. Thorp. 2002. Crop pollination from native bees at risk from agricultural intensification. Proceedings of the National Academies of Science 99: 16812–16816.

 [4] Biesmeijer, J.C., S. P. M. Roberts, M. Reemer, R. Ohlemüller, M. Edwards, T. Peeters, A. P. Schaffers, S. G. Potts, R. Kleukers, C. D. Thomas, J. Settele and W. E. Kunin. 2006. Parallel declines in pollinators and insect-pollinated plants in Britain and the Netherlands. Science 313: 351-354.

2 thoughts on “Habitat Fragmentation

  1. Pingback: the Paradise City Micro-Farm

  2. Pingback: Genomes and Diversity Blog- David Shmidt | Tackling the Nationwide Shortage of Bees

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