The importance of urban backgardens on plant and invertebrate recruitment: a field microcosm experiment

Private backgardens in cities have the capacity to enhance ecological function and connectivity. The importance of increased habitat availability was tested experimentally using microcosms with soil or with soil and vegetation added into Toronto backgardens. Local attributes of the backgardens were recorded, and within the microcosms, recruitment of seeds, plants, and winged and wingless invertebrates were recorded. Natural recruitment by all organisms was significant into the microcosms in the 20 backgardens tested. Invertebrate abundance and diversity, incidental seed recruitment, and aboveground vegetation growth was enhanced regardless of whether only bare soil was added or soil with vegetation. The number of woody plants (non-herbaceous plants with hard lignified tissues or woody parts e.g., stems and are adapted to survive from one year to the next i.e., through winter) in the backgardens predicted seed recruitment and number of plant species predicted winged invertebrate abundance. Hence, simple augmentation of private backgardens—even at an ecologically small-scale—can enhance the capacity of urban systems to provide appropriate habitats for organisms within a difficult matrix for many species.