The Effect of Increasing Connectivity for Urban Bee Populations -Hypothetical Proposal
An urban ecology proposal for a hypothetical project in Portland, Oregon focused on how the local genetic diversity of two native bumblebee species could would be affected by the increase of bioswales, ‘hell/healthstrip’ & median planting conversions. The goal of the project would be to use urban-greening & intentional plantings to address habitat fragmentation - creating connectivity pathways between populations that have become isolated due to urbanization. The native bumblebee species focused on in this proposal are the Obscure Bumblebee (Bombus caliginosus) & Yellow Bumblebee (Bombus fervidus) - both of which are listed by the ICUN Red List of Threatened Species as vulnerable/declining.
In addition to their vulnerable status spurring conservation strategies in urban areas, the generalist & crepuscular pollinating strategies of these species is important to community-level plant diversity in native plants as they’re one of the most effective native pollinators on a per-visit basis for both cultivated and wild plants. These species have large bodies - making them more active in cooler temperatures - and are more tolerant of low light foraging. These factors make them particularly effective pollinators in northern latitudes and high elevations. Genetic diversity and gene flow both drop when populations become more fragmented and isolated - as often happens due to urbanization structures including paving nesting grounds, shifting foraging planting options due to seasonality of blooms and increasing distance between nesting and foraging grounds.
This proposal is structured around the identification of species distribution patterns in Portland - determining 5 research areas and including community science observation efforts through bumblebeewatch.org for confirmation of species & abundance presence. Then the identification of potential connectivity pathways between research areas were found using a combination of zoning classifications, satellite view vegetation coverage for urban/suburban areas & perceived anthropocentric barriers to bee mobility in Portland (such as highways & lack of green space cover presence/potential). The research areas were labelled as Isolated (3x), Central (1x) and Control (1x) populations. The proposal explores a different connectivity pathway options between each Isolated area to the Central area, with no pathways proposed between the Control area and the Central area.
The goal of the proposal is not just to bolster conservation efforts through increased gene flow - it is also to identify the most effective strategy for connectivity pathways to implement throughout the city. The pathway options proposed include: 1) shifting planting regimes and greater implementation of bioswales, 2) median conversions and conscious plantings of ‘hell/healthstrips’ between sidewalks and streets, and 3) a combination of the two previous strategies. The efficacy of each connectivity strategy would be determined over a 10 year monitoring program in each research area & along the implemented connectivity option between each Isolated and the Central area through observation of species abundance yearly as well as sampling of each population for shifts in genetic diversity.
Please see the presentation below for more detailed descriptions & maps regarding the proposal.
