Caring for Pollinators - Bundesamt für Naturschutz

Steffan-Dewenter Pollinator declines and loss of pollination services
Drivers of pollinator loss
Several case studies identify habitat fragmentation and land use intensification as important
drivers of pollinator declines (Figure 3). The reduction of habitat area and the increase of
habitat isolation lead to lower species richness and abundance and shifts in community
composition. Particularly food plant specialists, cuckoo bees and small, solitary bee species
are affected by habitat fragmentation (Steffan-Dewenter & Westphal 2008). Interestingly, not
only local habitat characteristics but also the management of the wider landscape play a vital
role for pollinator diversity. Thus the implementation of adequate agri-environmental
schemes could contribute to the conservation of pollinators in agricultural landscapes
(Steffan-Dewenter & Westphal 2008, Meyer et al. 2008). The functional consequences of
pollinator declines for pollination of rare plants and crops are a controversially discussed and
still unsolved research question.
Fig. 3: The interplay of
pollination services, pollinators,
habitat fragmentation and land
use intensification (from Steffan-
Dewenter & Westphal 2008)
Consequences of pollinator declines for rare plant pollination
In the framework of the EU-project ALARM we developed a common study design and
protocols to evaluate the importance of population size, patch size and plant density on
flower visitation, pollinator diversity, and fruit or seed set. The research was performed in 5
European countries with altogether 10 focal rare plant species. The results show no effect of
overall population size but significant effects of patch area and patch density on flower
visitation rates and seed set. For five out of 10 plant species the data provide evidence for
significant pollination limitation (Dauber et al., submitted).
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