COS 56-6 - Grazing and ecosystem services: Effects of livestock herbivory on floral resources, pollinator populations and honey production in Mediterranean ecosystems

Tuesday, August 8, 2017: 3:20 PM
B110-111, Oregon Convention Center
Johannes Foufopoulos, School of Natural Resources & Environment, University of Michigan, Ann Arbor, MI and Scott Brenton, SNRE, University of Michigan Ann Arbor, Ann Arbor, MI

Livestock husbandry and apiculture both play integral roles for human societies across mediterranean regions of the globe. This study aims to (1) evaluate the impact of livestock grazing on Mediterranean vegetation structure and floral resources; (2) determine the relationship between grazing intensity and the productivity of managed honeybee hives, and; (3) determine the economic effects of grazing on apiculture.

We quantified vegetation condition and floral resources across a broad range of livestock grazing intensities in a Mediterranean phryganic ecosystem (Aegean Sea, Greece). We surveyed 14 study plots for grazing intensity and various vegetation structure and condition metrics. In a parallel sub-study we monitored beehive productivity by weighing beehives over the course of the summer, and analyzed vegetation condition and floral resources in the landscapes surrounding each beehive site. Lastly, we conducted surveys with beekeepers on each island to determine economic effects of livestock grazing on apiculture.


Grazing significantly impacts vegetation cover and floral resources, by disrupting brush canopy and reducing plant species richness, spring flower coverage, and vegetation biomass. However, cover of Conehead thyme (Coridothymus capitatus), the most important apicultural plant in the region, and a chemically defended taxon, benefitted from grazing and peaked at intermediate stocking rates. Thus, progressive increases in stocking rate reduced general flower cover and diversity, while simultaneously leading to denser thyme coverage. Beehive productivity during the main honey-producing period increased along both thyme cover and grazing intensity. However, beekeeper interviews revealed that grazing intensity was also positively correlated with higher amounts of supplemental feeding, elevated antiparasitic drug expenditures, and increased total costs. These expenses erased higher income from elevated thyme honey production in grazed areas. Comparison of the economic apiculture models on two neighboring islands (Naxos-heavily grazed; Paros-lightly grazed) revealed that beekeeping operations on Paros, by virtue of their lower costs, generated higher overall returns, despite producing less honey.

Although livestock grazing often promotes thyme populations, it tends to have an overall negative effect on apiculture operations. By expanding the scope of this study beyond first order metrics (honey production) to include previously externalized factors (beehive maintenance costs), we show any increases in thyme honey production in grazed regions are negated by concomitantly rising apiculture costs. Hence, light levels of grazing appear to be best suited for maintaining floral resources and maximizing returns from apiculture in the Mediterranean Sea region.