Adaptation tipping points of awetland under a drying climate

Wetlands experience considerable alteration to their hydrology, which typically contributes to a decline in their overall ecological integrity. Wetland management strategies aim to repair wetland hydrology and attenuate wetland loss that is associated with climate change. However, decision makers often lack the data needed to support complex social environmental systems models, making it difficult to assess the effectiveness of current or past practices. Adaptation Tipping Points (ATPs) is a policy-oriented method that can be useful in these situations. Here, a modified ATP framework is presented to assess the suitability of ecosystem management when rigorous ecological data are lacking. We define the effectiveness of the wetland management strategy by its ability to maintain sustainable minimum water levels that are required to support ecological processes. These minimum water requirements are defined in water management and environmental policy of the wetland. Here, we trial the method on Forrestdale Lake, a wetland in a region experiencing a markedly drying climate. ATPs were defined by linking key ecological objectives identified by policy documents to threshold values for water depth. We then used long-term hydrologic data (1978–2012) to assess if and when thresholds were breached. We found that from the mid-1990s, declining wetland water depth breached ATPs for the majority of the wetland objectives. We conclude that the wetland management strategy has been ineffective from the mid-1990s, when the region’s climate dried markedly. The extent of legislation, policies, and management authorities across different scales and levels of governance need to be understood to adapt ecosystem management strategies. Empirical verification of the ATP assessment is required to validate the suitability of the method. However, in general we consider ATPs to be a useful desktop method to assess the suitability of management when rigorous ecological data are lacking

Determining the probability of cyanobacterial blooms: the application of Bayesian networks in multiple lake systems

A Bayesian network model was developed to assess the combined influence of nutrient conditions and climate on the occurrence of cyanobacterial blooms within lakes of diverse hydrology and nutrient supply. Physicochemical, biological, and meteorological observations were collated from 20 lakes located at different latitudes and characterized by a range of sizes and trophic states. Using these data, we built a Bayesian network to (1) analyze the sensitivity of cyanobacterial bloom development to different environmental factors and (2) determine the probability that cyanobacterial blooms would occur. Blooms were classified in three categories of hazard (low, moderate, and high) based on cell abundances. The most important factors determining cyanobacterial bloom occurrence were water temperature, nutrient availability, and the ratio of mixing depth to euphotic depth. The probability of cyanobacterial blooms was evaluated under different combinations of total phosphorus and water temperature. The Bayesian network was then applied to quantify the probability of blooms under a future climate warming scenario. The probability of the "high hazardous" category of cyanobacterial blooms increased 5% in response to either an increase in water temperature of 0.8°C (initial water temperature above 24°C) or an increase in total phosphorus from 0.01 mg/L to 0.02 mg/L. Mesotrophic lakes were particularly vulnerable to warming. Reducing nutrient concentrations counteracts the increased cyanobacterial risk associated with higher temperatures

Environmental flow requirements of estuaries: providing resilience to current and future climate and direct anthropogenic changes

Estuaries host unique biodiversity and deliver a range of ecosystem services at the interface between catchment and the ocean. They are also among the most degraded ecosystems on Earth. Freshwater flow regimes drive ecological processes contributing to their biodiversity and economic value, but have been modified extensively in many systems by upstream water use. Knowledge of freshwater flow requirements for estuaries (environmental flows or E-flows) lags behind that of rivers and their floodplains. Generalising estuarine E-flows is further complicated by responses that appear to be specific to each system. Here we critically review the E-flow requirements of estuaries to 1) identify the key ecosystem processes (hydrodynamics, salinity regulation, sediment dynamics, nutrient cycling and trophic transfer, and connectivity) modulated by freshwater flow regimes, 2) identify key drivers (rainfall, runoff, temperature, sea level rise and direct anthropogenic) that generate changes to the magnitude, quality and timing of flows, and 3) propose mitigation strategies (e.g., modification of dam operations and habitat restoration) to buffer against the risks of altered freshwater flows and build resilience to direct and indirect anthropogenic disturbances. These strategies support re-establishment of the natural characteristics of freshwater flow regimes which are foundational to healthy estuarine ecosystems

Exploring, exploiting and evolving diversity of aquatic ecosystem models: A community perspective

Here, we present a community perspective on how to explore, exploit and evolve the diversity in aquatic ecosystem models. These models play an important role in understanding the functioning of aquatic ecosystems, filling in observation gaps and developing effective strategies for water quality management. In this spirit, numerous models have been developed since the 1970s. We set off to explore model diversity by making an inventory among 42 aquatic ecosystem modellers, by categorizing the resulting set of models and by analysing them for diversity. We then focus on how to exploit model diversity by comparing and combining different aspects of existing models. Finally, we discuss how model diversity came about in the past and could evolve in the future. Throughout our study, we use analogies from biodiversity research to analyse and interpret model diversity. We recommend to make models publicly available through open-source policies, to standardize documentation and technical implementation of models, and to compare models through ensemble modelling and interdisciplinary approaches. We end with our perspective on how the field of aquatic ecosystem modelling might develop in the next 5–10 years. To strive for clarity and to improve readability for non-modellers, we include a glossary

Twenty-three unsolved problems in hydrology (UPH) – a community perspective

This paper is the outcome of a community initiative to identify major unsolved scientific problems in hydrology motivated by a need for stronger harmonisation of research efforts. The procedure involved a public consultation through on-line media, followed by two workshops through which a large number of potential science questions were collated, prioritised, and synthesised. In spite of the diversity of the participants (230 scientists in total), the process revealed much about community priorities and the state of our science: a preference for continuity in research questions rather than radical departures or redirections from past and current work. Questions remain focussed on process-based understanding of hydrological variability and causality at all space and time scales. Increased attention to environmental change drives a new emphasis on understanding how change propagates across interfaces within the hydrological system and across disciplinary boundaries. In particular, the expansion of the human footprint raises a new set of questions related to human interactions with nature and water cycle feedbacks in the context of complex water management problems. We hope that this reflection and synthesis of the 23 unsolved problems in hydrology will help guide research efforts for some years to come

Tracing environmental and livelihood dynamics in a tropical coastal lagoon through the lens of multiple adaptive cycles

Understanding the long-term dynamics of social-ecological systems is critical to better inform sustainable management. Since Holling's adaptive cycle heuristic, published in 2001, substantial progress has been made to explore historical changes in agricultural, pastoral, and forest systems. However, the application of this heuristic in coastal fishery systems has been relatively rare. Using the Tam Giang Lagoon in Vietnam as an example of a rapidly changing environment, we explore the historical behavior of this tropical coastal social-ecological system (SES), associated livelihood pathways, and possible challenges for future livelihood adaptations through the lens of the adaptive cycle metaphor. Our analysis demonstrates that the present lagoon SES condition is the result of a series of historical events and reorganization attempts through two complete adaptive cycles. The lagoon's future vulnerability is tied to the intensification of human uses, prolonged ecological degradation, and intensifying climatic hazards. We show how the evolution of the lagoon SES resulted in divergent livelihood pathways that bring benefits to some users but also cause persistent constraints and sometimes irreversible losses to other users in shared common pool resources. A one-size-fits-all fishery management approach is therefore ill-suited for improving diverse livelihoods. We recommend that fishery policies take seriously the heterogeneity in livelihood pathways for sustainable lagoon management. We end by reflecting on the usefulness of the adaptive cycle heuristic in systematically exploring historical dynamics and identifying underlying drivers and feedbacks between the social and ecological components of complex fishery systems

The development and application of improved solids modelling to enable resilient urban sewer networks

Decreasing per capita water consumption in several OECD countries has led to a notable flow reduction into sewer systems. However, sewers still transport similar quantities of solids and pollutants, leading to increased wastewater concentration and, potentially, excess solids deposition. The shift towards decentralised water schemes in cities and widely reported changes in rainfall patterns cast additional uncertainty on future wastewater quality and flows into sewers. Excess solids deposition in sewers can cause increased environmental pollution risks at Combined Sewer Overflows from solids resuspension and reduced sewer hydraulic capacities. This review analyses the magnitude of excess solids deposition due to changing wastewater composition and evaluates current approaches to modelling sewer solids. Gaps in commonly used modelling approaches for deposited bed processes, specifically in bed consolidation and bed particle cohesion processes, and gross solids transport were identified and addressed to enable better solids risk prediction and management