The Road Not Taken

We all have our life-fork stories, those crossroads where we could have gone one way but chose another.

I was reminded about one of my road-not-taken moments last week, at the Entomological Society of America (ESA) meetings in Portland, Oregon. My 1975 crossroads decision was whether to go to the University of Kansas and study killer honeybees in South America with Chip Taylor, or to Cornell University and work with Richard Root, studying the effects of crop diversity on beneficial insects such as unmanaged wild pollinators.

Killer bees won out, and I’ve never regretted that decision, but was intrigued to see a wave of studies presented at the ESA meeting demonstrating how habitat heterogeneity is important for the diversity and abundance of wild bees.

The role of habitat diversity as a key factor in maintaining wild bee populations has become one of those hot topics that attract the talented scientists who gravitate to the interesting questions. It’s a challenging research area, requiring sophisticated methods to measure and compare habitat heterogeneity with bee diversity and abundance, all in environments heavily altered by the human impact of farming.

Two research approaches have converged with the same result. The first, sampling bees in a range of simple to complex habitats, has clearly demonstrated that contemporary agriculture is barren for wild bees.

Industrial agriculture is a dead zone for beneficial pollinators due to vast acreages of monocropped plantings kept clear of weeds with herbicides, and limited natural habitats adjacent to farmland in which bees can feed and nest. Wild bees rely on plants whose flowering seasons adjoin each other to provide extended availability of nectar and pollen, as well as on undisturbed nesting sites, neither of which are found in and around today’s habitat-deforming farms.

The second line of research has been more experimental, planting bee-friendly hedgerows and ground cover at farm sites and examining whether wild bee populations increase and thrive. The results of these multi-year studies so far have been encouraging, often showing dramatic increases in pollinators as habitat diversifies.

There is another research direction that is difficult but necessary to make the case for habitat reconstruction to enhance pollinator populations: economic analyses. So far, there have been few studies asking that final dollar value question: Does increased diversity and abundance of wild bees lead to more pollen transferred between flowers, to better seed set, to heavier crop weight, and finally to higher yields and increased income sufficient to justify the costs of habitat improvements?

A student in my laboratory, Lora Morandin, did one such economic study a number of years ago in canola fields in northern Alberta. Her research demonstrated that a high variety of wild plants in and near farmland were associated with more diverse and abundant bee populations that increased canola yield. Farmers who planted their entire field earned about $27,000 in profit per farm, whereas those who left a third unplanted for bees to nest and forage in earned $65,000 on a farm of similar size, due simply to better pollination.

The causes of reduced plant biodiversity on farms are clear, and the solutions easily envisioned and implemented. The two most destructive factors for bees are overly large single cropped acreages and the use of herbicides that clean fields of weeds.

The solutions? Increase farm diversity through multiple crops, reduce herbicide use to allow more flowering weeds in farm fields and plant non-crop vegetation adjacent to farmland.

The encouraging news is that state and federal governments in the United States are beginning to fund bee conservation projects designed to increase bee diversity through habitat renovations. The dollar values are small, and the projects highly localized, but it’s a start.

Fundamentally, we’re faced with choosing between habitat-based farming that uses ecosystem services to pollinate crops, or chemically based industrial farming that harms habitats and requires managed pollinators, usually honeybees, to be brought into the crop to do the job that wild bees could probably do better.

If I were choosing today, biodiversity would be the cornerstone upon which I would build a research career. It makes more sense to enhance the natural diversity and services that ecosystems could provide than to stay on today’s treadmill of high input, low profit and environmentally damaging farming.