Climate change, increasing agricultural land use, and invasive species threaten freshwater ecosystems and their native biota.  The nexus of these threats are well documented in the Pacific Northwest of the United States, where Pacific salmon have declined over the past century and are facing increasing extinction risk.  Elevated stream temperature is one of the most pervasive water quality issues in this region, and projected climate change and riparian vegetation loss are predicted to exacerbate this problem.  Rising temperatures have direct implications for coldwater native salmon, but they will also alter the composition of aquatic biota by facilitating the range expansion and altering the impacts of warmwater invasive species.  In an effort to address this challenge, this project develops and applies an analytical framework that quantifies how future climate change and riparian land use influences the direct and indirect effects of invasive species on the survival of native salmonids in the John Day River, Oregon.  By integrating climate-change projections, geomorphic sensitivity, riparian land use, stream thermodynamics, and ecological niche modeling, this project quantifies the potential range expansion and temperature-mediated impacts of invasive species in critical habitats that support native fishes, including endangered Chinook salmon (Oncorhynchus tshawytscha). This project is funded by an EPA STAR grant.

Predicting the vulnerability of lake ecosystems to invasive crayfish and snails

Government bodies ranging from local to federal have been attempting to design management strategies to reduce the negative environmental, economic, and human health impacts of invasive species.  The task is daunting: landscapes to be managed are vast, there are numerous invasive species, and funding for invasive species management is limited.  Prevention is widely recognized as the cornerstone of most invasive species management strategies.  The importance of preventing the secondary spread of invasive species is particularly relevant in freshwater ecosystems of Washington because of the large network of lakes that support a rich diversity of biological life.  Washington lakes are home to more than one hundred invasive species, many of which threaten both socially- and economically-important native plants and animals.  The Olden laboratory at the University of Washington has initiated a comprehensive investigation of the present-day distribution of red swamp crayfish (Procambarus clarkii), virile crayfish (Orconectes virilis) and Chinese Mystery Snail (Bellamya chinensis) in lakes of Washington with the aim of developing predictive models identifying those ecosystems vulnerability to future invasions. Our studies are also examining the food web consequences of these invasions. 

Developing regional environmental flow standards for Washington State

Despite Washington's reputation as a perpetually rainy place, the water needs of people and natural ecosystems are increasingly in conflict. Water managers are becoming increasingly cognizant of these pressures, yet there remains a critical knowledge gap of the ecological tradeoffs associated with various flow management practices, including instream flows as presently mandated in Washington. This project aims to advance the science and develop the tools required for ecologically sustainable water management in Washington. Our approach is following the Ecological Limits of Hydrologic Alteration (ELOHA) framework by synthesizing the knowledge and data collected from individual rivers into a scientific framework that supports and guides the development of environmental flow standards at the regional scale. We are developing a state-wide hydrologic classification of unregulated rivers and quantifying the range of natural flow variation that regulates characteristic ecological processes and habitat characteristics for distinct hydrologic types.  This will provide a baseline or reference condition against which ecological responses to alteration can be measured across multiple river segments falling along a gradient of dam- and climate-induced hydrologic modification.  These results will highlight the ecological effects of hydrologic alteration and help form the basis of flow management for both river ecosystem protection (proactive flow management) and sustainable restoration (reactive flow management) for riverine biodiversity. This project is funded by NOAA Fisheries.

Desert fish ecology in the Lower Colorado River Basin

The Colorado River played a pivotal role in the settlement, growth and economic development of the American Southwest. Efforts to tame the Lower Colorado River began soon after the arrival of western Europeans, and today hundreds of dams and diversion structures have created one of the most controlled rivers on Earth. Environmental change in the form of land-use and river regulation has facilitated the widespread invasion of non-native fish species that prey on and compete with native fishes. Anticipating the future threatens posed by invasive species requires a predictive, proactive approach that forecasts potential distributions to further inform the identification and prioritization of critical conservation areas and endemic species at risk. In collaboration with the Lower Colorado River Basin (USGS) Aquatic GAP Project (http://www.lcrgap.org/) this project is forecasting the potential distributions of freshwater non-indigenous fish species in the Lower Colorado River Basin as a function of current and project future environmental conditions. This project is funded by the U.S. Geological Survey.

Conservation biogeography of freshwater fishes

Ecologists are now challenged to reconcile the historical biogeography of long-evolved native species with the emerging and rapidly expanding patterns of recently arrived non-indigenous species.  In contrast to vagile terrestrial species, freshwater fishes are uniquely constrained because their ability to respond to environmental change is limited to movement defined by the connectivity of water.  In recent times, however, humans have dramatically enhanced the ability of fish species to overcome these natural biogeographic barriers to movement either through intentional transport and other colonization routes created by anthropogenic activities. By dissolving physical barriers to movement and connecting formerly-isolated regions of the world, human-mediated species introductions have dramatically reshuffled the present-day biogeography of freshwater fishes.  The nature of this biological re-organization is deceptively complex because it involves the simultaneous processes of species invasions and extinctions operating in response to natural and human-induced environmental change. An active research area in the Olden Lab involves examining the patterns, mechanisms and environmental drivers of biotic homogenization at a variety of spatial scales for an array of taxonomic groups, and exploring the associated ecological, evolutionary and social implications.

Hydroecology and fish conservation in Australia

Although relatively depauperate by world standards with a little over 200 species, the Australian freshwater ichthyofauna has long been recognized as distinctive to the rest of the world. Many of the Australian freshwater fishes, although presumably well adapted to the harsh environment and pronounced seasonal fluctuations experienced in many parts of Australia, show little evidence of specialization, and lack the diversity of life-histories and characteristics of many other continents. Consequently, Australia’s freshwater ecosystems are thought to be particular vulnerable to environmental alteration and invasive species. The Olden laboratory is currently working with Mark Kennard and Brad Pusey at Griffith University on a number of projects examined the interface between riverine hydrology, climate change, invasive species, and the community ecology of native species. These projects include:

1. Examining the potential ecological impacts of changes in dry season flow regimes caused by water resources development in the Daly River catchment in the Northern Territory .

2. Forecasting the effects of projected climate change on freshwater fish biodiversity.

3. Developing a hydrologic classification of Australian rivers.

4. Exploring fish-environment relationships for eastern coastal streams.

These projects involve collaborations between Griffith University (Mark Kennard, Brad Pusey), Charles Darwin University (Michael Douglas), CSIRO Sustainable Ecosystems, the Northern Territory Government, the Wagiman people, and the Guwardugan Rangers and the Wardaman Aboriginal Corporation. This project is funded by Land and Water Australia, the Natural Heritage Trust and TRaCK (Tropical Rivers and Coastal Knowledge research hub).