Uncovering the ecosystem service legacies of wetland loss using high-resolution models

Abstract

Ecosystem services provided by contemporary landscapes are different from those of the past, and this difference is influenced by the legacies of policies that incentivized wetland drainage without considering the impact on ecosystem services. Heterogeneity in ecosystem service legacies is rarely acknowledged or documented. Even less understood is the relative role of historical wetland type (e.g., swamps, fens) and contemporary land cover in shaping these heterogeneous outcomes. Here, we contrasted contemporary ecosystem services with a scenario of no wetland drainage in the Ruamahanga Basin, New Zealand, a region historically rich in wetlands. Using the high-resolution Land Use Capability Indicator model, we mapped nitrogen retention, phosphorous retention, sediment retention, agricultural productivity, and flood mitigation at a 5-m spatial resolution under these two scenarios. Our work supports the broad understanding that agricultural productivity has increased in contemporary landscapes, while flood mitigation and nutrient retention have decreased. Net losses in ecosystem services occurred for the majority of historical wetlands, while net gains were less common. However, spatially heterogeneous and divergent responses of ecosystem services to land cover changes reinforced the need for high-resolution models to untangle the range of factors affecting ecosystem service provisioning. Contemporary land cover explained very little variation in ecosystem services. Initial conditions, however, played an important role in determining ecosystem service outcomes with losses of swamps being particularly problematic for net loss of ecosystem services provisioning. The maps we produced, and the algorithms underlying them, provide tools to envision both local- and broad-scale effects of historical wetland drainage.