Issues in urban / suburban biodversity studies

Human land-use alters soils differently depending on the intensity and type of use, often resulting in persistent temporal effects known as legacy effects. Cities, which are complex socio-ecological landscapes, are expected to be rich in legacy effects due to the co-occurrence of multiple development trajectories. However, few urban ecological studies consider the role of history in shaping contemporary biodiversity patterns belowground since many are discouraged to work on a study system that is impractical, i.e., no ease of access to things that are underfoot; or, to work on a study organism that is too small to see, i.e., needing the assistance of microscopes. We therefore asked: does soil biodiversity in our present-day urban greenspaces differ due to varied historical land-use? We surveyed earthworms in 25 urban parks across the island of Montreal, Quebec, Canada with three former land-uses: industrial, agricultural, and forested. We predicted that parks with a forested historical land-use would host the greatest earthworm biodiversity, followed by parks with agricultural and then industrial historical land-use. We measured and calculated the following biodiversity metrics: abundance, density, biomass, taxonomic richness, and Simpson’s Diversity Index. Our preliminary findings suggest that earthworm biodiversity in urban greenspaces do not necessarily respond to legacy effects by historical human land-use. Rather, more important local factors such as soil pH, soil moisture, and dominant vegetation might be greater drivers of earthworm biodiversity. As ecosystem engineers, earthworms can significantly modify their surrounding environment by their burrowing and feeding action. Through this, earthworms facilitate the establishment of and offer support to the soil biological community at large. Therefore, understanding what determines earthworm biodiversity in cities may invariably increase human welfare by stewarding our urban soils.

We live in an increasingly urban world. The form of urban areas affects how much natural habitats remain and how animals can move between them and maintain the genetic diversity of their populations. Making urban planning compatible with biodiversity conservation is an urgent need and requires that we understand how urban forms affect biodiversity. In the research I will present, we assessed the interactions between urban forms, habitat connectivity and simulated genetic diversity across 325 European cities. We showed that urban sprawl, everything else being equal, tends to reduce genetic diversity. I will discuss how this should influence urban planning if we are to prevent biodiversity from collapsing in and around cities.

European buckthorn (Rhamnus cathartica) is an invasive shrub that has detrimental effects on forest ecosystems in southern Ontario because it outcompetes and restricts native plant regeneration. Buckthorn typically establishes in areas with open space and high light availability, such as forest canopy gaps, but is limited by forest stands with high ecological integrity. This study investigates (i) whether buckthorn occurrence and abundance in forest canopy gaps are influenced by gap size and gap age, and (ii) the role that ecological integrity plays in this relationship. A principal components analysis (PCA) was used to create two indices of ecological integrity: forest fragment integrity and species composition integrity. A binomial generalized linear mixed model (GLMM) was used to model buckthorn occurrence and a negative binomial GLMM was used to model relative buckthorn abundance across thirty-seven canopy gaps in public forest stands in London, ON. The results did not provide evidence that buckthorn occurrence or abundance are responsive to gap size, gap age, forest fragment integrity, or species composition integrity. The results may have been influenced by ongoing buckthorn removal across study sites and limitations to aerial photographs used to age canopy gaps; future studies may consider the use of sites with varying types of management, and the use of multiple methods to age gaps. Ultimately, buckthorn growth may not be responsive to the size and age of canopy gaps as predicted in this study, and future studies may consider investigating the influence that seed dispersal by birds has on the invasibility and dominance of buckthorn in forest ecosystems.

Protection Island, British Columbia, a suburb of the City of Nanaimo with a relatively high density of humans, is an environment where river otters conflict with humans over the use of space and are viewed as a nuisance species. I examine human-otter coexistence and habitat suitability and selection in this relatively urban environment. I examine differences, and their underlying causes, in attitude and perception towards otters among residents, while contextualizing them within the critical animal geographies and conservation management literatures. Further, using GPS habitat surveys and presence-absence data, I apply maximum entropy modelling to predict otter space use in their environment so we can promote human-otter coexistence.