Ecosystem services in connected catchment to coast ecosystems: Monitoring to detect emerging trends.

There is an increasing need for long-term monitoring of ecosystems and their services to inform on-ground management. The supply of many ecosystem services relies on connections that span multiple ecosystems. Monitoring the underlying condition of interconnected ecosystems is therefore required to track effectiveness of past interventions and identify impending change. Here we test the performance of indicators of ecosystem services with the aim of identifying the time-scales over which indicators of ecosystem services responded to change. We chose a case-study of a catchment in Northern Australia, where water resource development is a threat to the river flows that support vegetation growth and the life-cycle of coastal fishery species. We developed a novel approach to performance testing that drew on state-space modelling to capture ecological dynamics, and structural equation modelling to capture covariation in indicator time series. We first quantified covariation among three ecological indicators that had time-series data: pasture biomass, vegetation greenness and barramundi catch per unit effort. Higher values of all indicators occurred in years with greater river flow. We then predicted the emergence times for each indicator, as the time taken for a trend in an indicator to emerge from the background of natural variation. Emergence times were > 10 years in all cases, quantified at 80 % and higher confidence levels. Past trends and current status of ecosystem service flows are often used by decision makers to directly inform near-term actions, particularly for provisioning services (such as barramundi catch) due to their important contribution to regional economies. We found that ecological indicators could be used to assess historical performance over decadal timespans, but not as short-term indicators of recent change. More generally, we offer an approach to performance testing of indicators. This approach could be useful for quantifying timescales of ecosystem response in systems where cross-ecosystem connections are important.

Challenges in modelling the sediment retention ecosystem service to inform an ecosystem account - Examples from the Mitchell catchment in northern Australia.

A systems analysis perspective related to soil science is necessary to achieve many of the sustainability targets articulated by the United Nations Sustainable Development Goals (SDGs). The System of Environmental-Economic Accounting - Ecosystem Accounting (SEEA-EA) framework is the international statistical standard for quantifying both the contributions that ecosystems make to the economy, and the impacts of economic activity on ecosystems. However, due to the difficulty of obtaining empirical data on ecosystem service flows, in many cases such quantification is informed by ecosystem service models. Previous research on the Mitchell catchment, Queensland Australia provided a novel opportunity to quantify the implications of using a model of hillslope erosion and sediment delivery in isolation (as represented in one of the most frequently used ecosystem service models - InVEST), by comparing such estimates against multiple lines of local empirical data, and a more comprehensive representation of locally important erosion and deposition processes through a sediment budget model. Estimates of the magnitude of hillslope erosion modelled using an approach similar to InVEST and the calibrated sediment budget differed by an order of magnitude. If an uncalibrated InVEST-type model was used to inform the relative distribution of erosion magnitude, findings suggest the incorrect erosion process would be identified as the dominant contributor to suspended sediment loads. However, the sediment budget model could only be calibrated using data on sediment sources and sinks that had been collected through sustained research effort in the catchment. A comparable level of research investment may not be available to inform ecosystem service assessments elsewhere. Findings for the Mitchell catchment demonstrate that practitioners should exercise caution when using model-derived estimates of the sediment retention ecosystem service, which have not been calibrated and validated against locally collected empirical data, to inform an ecosystem account and progress towards achieving the SDGs.

Vegetation and longitudinal coarse sediment connectivity affect the ability of ecosystem restoration to reduce riverbank erosion and turbidity in drinking water.

It is a substantial challenge to quantify the benefits which ecosystems provide to water supply at scales large enough to support policy making. This study tested the hypothesis that vegetation could reduce riverbank erosion, and therefore contribute to reducing turbidity and the cost of water supply, during a large magnitude flood along a 62 km riparian corridor where land cover differed substantially from natural conditions. Several lines of evidence were used to establish the benefits that vegetation provided to reducing eleven riverbank erosion processes over 1688 observations. The data and analyses confirmed that vegetation significantly reduced the magnitude of the riverbank erosion process which was the largest contributor to total erosion volume. For this process, a 1% increase in canopy cover of trees higher than five metres reduced erosion magnitude by between 2 and 3%. Results also indicate that riverbank erosion was likely to be affected by direct changes to the riparian corridor which influenced longitudinal coarse sediment connectivity. When comparing the impact of these direct changes on a relative basis, sand and gravel extraction was likely to be the dominant contributor to changed erosion rates. The locations where erosion rates had substantially increased were of limited spatial extent and in general substantial change in river form had not occurred. This suggests that the trajectory of river condition and increasing turbidity are potentially reversible if the drivers of river degradation are addressed through an ecosystem restoration policy.