A Riverine Ecosystem Service Cascade Model (RESCaM) framework for assessing ecosystem service provision as applied to English geomorphic river types

Abstract

Riverine ecosystems are considered the lifeblood of the Earth and because of this, have been exploited for centuries for social, agricultural and industrial development, resulting in their environmental degradation and simplification. This has led to a shift in the natural processes and functions and thus their ability to provide a full range and overall high levels of regulating, provisioning and cultural ecosystem services, which humans rely on. An ecosystem service and nature-based approach is being increasingly recognised as a useful tool to help evaluate, protect and restore river ecosystems for maximising the delivery of ecosystem services sustainably. Riverine ecosystem services are derived from riverscapes whereby "hydrological, geomorphological and ecological linkages and pathways of water, sediment and biogenic matter drive the relationship between river processes and physical habitat character and ecosystem services" (Large and Gilvear, 2015; Thorp et al., 2006). Better integration of this understanding is needed to inform sustainable river management in the 21st Century and maximise ecosystem services. This research aims to develop a bespoke riverine ecosystem service assessment methodology, for rivers in England, recognising the biophysical structure of river ecosystems as the template upon which ecosystem services are generated and is useful in guiding future river management. First, I start by critically evaluating an existing river ecosystem service assessment methodology using the Google EarthTM (GE TM) platform, as proposed by Large and Gilvear (2015). The assessment is applied to a variety of rivers across England and Wales representing differing characteristics, scales and land cover uses and validated through field survey. I conclude that the L&G2015 methodology is not suitable for useful application across English and Welsh river networks and that significant advances and refinements are required. The research then focuses on developing a bespoke riverine ecosystem service assessment methodology for English and Welsh rivers that (i) accounts better for their geomorphological character, (ii) uses datasets are available in English and Welsh context and (iii) is underpinned by an evidence-based linkage matrix which recognises positive and negative linkages between riverscape attributes and land cover types, natural ecosystem functioning and ecosystem service provision. The linkages have been identified through an extensive literature review and each linkage has been assigned a confidence level. The linkages have been placed within a Riverine Ecosystem Service Cascade Model (RESCaM) framework. A geomorphic river type classification, recognising thirteen geomorphic river types commonly found in England, is further integrated within the approach to provide the template for which to evaluate ecosystem service ‘performance’ at the river reach-scale. The approach is tested across the spectrum of river types found in England and Wales and its significance for policy and river management is discussed.