Fragmented landscapes affect honeybee colony strength at diverse spatial scales in agro-ecological landscapes in Kenya

Landscape fragmentation and habitat loss at multiple scales directly
affect species abundance, diversity and their productivity. There is a
paucity of information about the effect of the landscape structure and
diversity on honeybee colony strength in Africa. Here, we present new
insights into the relationship between landscape metrics such as patch
size, shape, connectivity, composition and configuration and honeybee
(Apis mellifera) colony strength characteristics. Remote sensing-based
landscape variables were linked to honeybee colony strength variables in a
typical highly fragmented small holder agro-ecological region in Kenya. We
examined colonies in six sites with varying degrees of land degradation,
during the period from 2017 to 2018. Landscape structure was first mapped
using medium resolution bi-temporal Sentinel-1 and Sentinel-2 satellite
imagery with an optimized random forest model. The influence of the
surrounding landscape matrix was then constrained to two buffer distances
i.e., 1 km representing the local foraging scale and 2.5 km representing
the wider foraging scale around each investigated apiary and for each of
the six sites. The results of zero-inflated negative binomial regression
with mixed effects showed that lower complexity of patch geometries
represented by fractal dimension and reduced proportions of croplands were
most influential at local foraging scales (1 km) from the apiary. In
addition, higher proportions of woody vegetation and hedges resulted in
higher colony strength at longer distances from the apiary (2.5 km).
Honeybees in moderately degraded landscapes demonstrated the most
consistently strong colonies throughout the study period. Efforts towards
improving beekeeper livelihoods, through higher hive productivity, should
target moderately degraded and heterogeneous landscapes, which provide
forage from diverse land covers.