Building Carbon Storage and Resilience to Extreme Climate Events into River Management

Abstract:

Traditional river management focuses on altering channel form and fluxes of water and sediment to maximize physical homogeneity, downstream conveyance, and stability. As the negative consequences of traditional management have become increasingly problematic, management has shifted toward re-introducing heterogeneity. This heterogeneity can take the form of physically complex channel boundaries, lateral and vertical connectivity within the river corridor (channel and floodplain), more natural water and sediment regimes, and room for rivers to adjust to temporally variable influxes of water and sediment. We explore how heterogeneity within river corridors influences (i) organic carbon storage in the form of large wood and floodplain sediment and (ii) the resilience of the river corridor to extreme climate events (i.e., ability to physically and ecologically recover from extreme events). We find that greater heterogeneity promotes carbon storage and resilience. The limited research conducted thus far indicates that differences in carbon storage and resilience between river networks reflect differences in flow and historical disturbance regimes, network configuration, and biome. Low-relief catchments at high latitudes may be disproportionately important in carbon storage, although climate warming and the associated permafrost thaw and changing precipitation regimes may be reducing their resiliency to extreme climate events. Spatial differences in carbon storage and resilience within a river network largely reflect differences in geomorphic context, as defined by valley and channel geometry and associated connectivity. Portions of a network in which geomorphic context facilitates floodplain wetlands have disproportionately high carbon storage and resilience to extreme climate events. Differences in carbon storage and resilience at all spatial scales also strongly reflect contemporary and historic land uses, with more highly altered rivers typically having lower carbon storage and less resilience. River management that emphasizes identification of the portions of river networks that maximize carbon storage and resilience, as well as the conditions that create and maintain storage and resilience, is critical to maintaining the vitality of river ecosystems under a changing climate.