Hydro-bio-geo-socio-chemical interactions and the sustainability of residential landscapes

Abstract

Residential landscapes are essential to the sustainability of large areas of the United States. However, spatial and temporal variation across multiple domains complicates developing policies to balance these systems' environmental, economic, and equity dimensions. We conducted multidisciplinary studies in the Baltimore, MD, USA, metropolitan area to identify locations (hotspots) or times (hot moments) with a disproportionate influence on nitrogen export, a widespread environmental concern. Results showed high variation in the inherent vulnerability/sensitivity of individual parcels to cause environmental damage and in the knowledge and practices of individual managers. To the extent that hotspots are the result of management choices by homeowners, there are straightforward approaches to improve outcomes, e.g. fertilizer restrictions and incentives to reduce fertilizer use. If, however, hotspots arise from the configuration and inherent characteristics of parcels and neighborhoods, efforts to improve outcomes may involve more intensive and complex interventions, such as conversion to alternative ecosystem types.

Fig. 1.

Interactions between hydrologic, biogeochemical, landscape structure, and social factors control nitrogen export from lawns and residential landscapes in a coupled natural human systems decision-making framework. Household-level management practices (A) influence nitrogen export (B), but these practices play out on a hydro-bio-geo-chemical template with varying susceptibility/vulnerability to nitrogen loss. Variation in export outcomes leads to the formulation of policies and implementation (C), but the adoption of these policies by homeowners/lawn managers (D) is influenced by social factors and communication approaches.

Fig. 2.

Human management interacts with hydrogeomorphic features both within and between parcel structures that greatly influence the offsite environmental impact of parcel management at large scales. These features include nonresidential parcels such as riparian areas, stream corridors, and drainage swales (in blue) and storm sewers (white) that cross parcel boundaries.

Fig. 3.

Significant functional variation in suburban front yards, driven by topography, influences sources (mineralization) and sinks (denitrification potential, DNP) of nitrogen and water (infiltration) within residential parcels. Different letters denote significant differences at P < 0.05. Error bars indicate ±1 S.E. Adapted from Suchy et al. (34).

Fig. 4.

Significant functional variation in residential parcels, driven by neighborhood (exurban, suburban), front yard versus backyard (FY versus BY), institutional management (Inst.), and fertilizer application, influences sources (mineralization) and sinks (denitrification potential, DNP) of nitrogen and water (infiltration) within residential parcels. Different letters denote significant differences at P < 0.05. Error bars indicate ±1 S.E. Adapted from Suchy et al. (34).

Fig. 5.

Nitrate flux in runoff and leachate for hydro-bio-geo-chemical “hotspot” groups of fertilized lawns. Different letters denote significant differences at P < 0.05. Group 1, which is comprised of sampling locations with low saturated infiltration rates (SInf) and low denitrification potential (DNP), has the highest potential to function as a hotspot of nitrogen export. Group 2 is high SInf and low DNP; group 3 is low SInf and high DNP; group 4 (lowest potential to function as a hotspot of export) is high SInf and high DNP. Error bars indicate ±1 S.E. Adapted from Suchy et al (35).