Effects of Livestock Grazing on Honey Production in a Mediterranean Rangeland Ecosystem

honey;mediterranean;Greece;Natural Resources and Environment

Brenton, ScottHardin, Rebecca ;

University of Michigan

关键词: honey;    mediterranean;    Greece;    Natural Resources and Environment;   

Others  :  https://deepblue.lib.umich.edu/bitstream/handle/2027.42/123033/Scott%20BrentonThesis%20Final.pdf?sequence=1&isAllowed=y

瑞士|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Livestock husbandry has played an integral role for human societies in the Mediterranean Basin.While ruminant grazing traditionally comprised part of diverse agrosilvopastoral systems, inrecent decades it has experienced substantial intensification in Mediterranean countries due toEuropean Union subsidies and production for international markets. Apiculture has also playedan important role in rural Mediterranean livelihoods for millennia, and is important globally bothfor apicultural products and crop pollination. Honeybees have faced worldwide losses in recentdecades, along with a decline of floral resources, although the drivers of these changes are notwell understood. The aim of this study is to (1) evaluate the impact of livestock grazing onMediterranean vegetation structure and floral resources; (2) determine the relationship, betweengrazing intensity and the productivity of managed honeybee hives, and; (3) determine theeconomic effect, if any, that overgrazing has on apicultural activities in the region.Methods. I measured vegetation condition and floral resources across a broad range of livestockgrazing intensities in a Mediterranean phryganic ecosystem on the islands of Naxos and Paros inthe Aegean Sea (Greece). 14 study plots were surveyed, and the vegetation metrics of canopygap, basal gap, vegetation height, plant species richness, spring flower coverage, thyme flowercoverage, and thyme bush coverage were measured. As a proxy for grazing intensity, I usedstocking rates, as well as biomass removed by grazers, quantified as the amount of ruminantdung collected along standardized transects. I monitored beehive productivity by weighingbeehives every 10 to 14 days over the course of the summer flowering season. I establishedtransects in the vicinity of the beehives, and repeated the same vegetation measurements used inthe 14 study plots to determine vegetation condition around each beehive site. Mixed modelswere utilized in order to determine the relationship between beehive productivity andsurrounding vegetation characteristics. In addition, I conducted surveys with a majority ofbeekeepers on each island to determine potential economic effects of grazing intensity onapiculture.Results. I found grazing to significantly impact vegetation cover and floral resources. Canopygap and basal gap sizes were positively correlated with grazing intensity, while plant speciesrichness was negatively associated with grazing intensity. Standing vegetation biomassdecreased with increased grazing intensity, whether quantified as stocking rate or amount ofplant matter consumed. Spring flower coverage also decreased with amount of plant matterconsumed by livestock. However, cover of Conehead thyme (Coridothymus capitatus), the mostimportant apicultural plant in the region, and a chemically defended taxon, actually benefittedfrom light to intermediate grazing conditions and followed a hump-shaped curve peaking atintermediate stocking rates. As a result, progressive increases in stocking rate had mixed effectson floral resources, leading to an overall reduction in general flower cover and diversity, whilesimultaneously leading to denser populations of thyme. Mixed models revealed that beehiveproductivity during the main honey-producing period was positively associated with increasedthyme flower area, stocking rate, thyme bush area, canopy gap, and basal gap (in decreasingorder of importance). Interviews with beekeepers also revealed that grazing intensity waspositively correlated with the need for higher amounts of supplemental bee food outside the shortsummer thyme season, elevated antiparasitic drug expenditures, as well as increased total costs(including feed, drug, labor and hive replacement expenditures). These expenses erased higher iiiincome from elevated thyme honey production in grazed areas. Notably, the surveys showed nocorrelation between grazing intensity and net profits. As a matter of fact, comparison of theeconomic apiculture models on the neighboring islands of Naxos (mostly heavily grazed) andParos (mostly ungrazed) revealed that beekeeping operations on Paros, by virtue of their lowercosts, generated higher overall returns, despite producing less honey.Conclusions. This study highlights the central importance of C. capitatus, a prolific nectarproducingspecies, for honey production in the Aegean. Despite the fact that C. capitatus benefitsfrom low to intermediate levels of grazing, due to competitive release, livestock husbandry haslargely negative effects on apiculture in the Aegean. By extending the scope of this study beyondthe traditionally considered first order metrics (honey production) to include additional factors(previously externalized beehive maintenance costs), I show any increases in thyme honeyproduction in grazed regions are negated by concomitant increased costs for bee food, drugs,labor and elevated beehive replacement rates. Thus my data suggest that light levels of grazingare best suited to maximize economic returns from apiculture in the Aegean Sea region.