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Aim Determining the spatial‐temporal spread of an invasive plant is vital for understanding long‐term impacts. However, invasions have rarely been directly documented given the resources required and the need for substantial foresight. One method widely used is historical photography interpretation, but this can be hard to verify. We attempt to improve this method by linking historical aerial photos to a paleobotanical analysis of pollen cores. Location Laurentian Great Lakes coastal wetlands, United States of America. Methods We chose invasive cattail ( Typha) as our model species because it is identifiable from aerial imagery and has persistent, identifiable pollen, and its ecological impacts appear to be time‐dependent. We used Geographic Information Systems, aerial photo‐interpretation and field verification to post‐dict the invasion history of Typha in several wetland ecosystems. Using 210 Pb and 137 Cs sediment dating and pollen classification, we correlated the temporal dominance of Typha to our estimates of per cent coverage at one site. The pollen record was then used to estimate the Typha invasion dynamics for dates earlier than those for which aerial photos were available. Results Typha spread through time in all study wetlands. Typha pollen dominance increased through time corresponding with increased spatial dominance. Hybrid cattail, T. × glauca increased in pollen abundance relative to T. angustifolia pollen through time. Main conclusions This study illustrates the value of generating historical invasion maps with publically available aerial imagery and linking these maps with paleobotanical data to study recent (< 100 years) invasions. We determined rates of Typha expansion in two coastal wetland types, validated our mapping methods and modelled the relationship between pollen abundance and wetland coverage, enhancing the temporal precision and breadth of analyses. Our methodology should be replicable with similar invasive plant species. The combination of pollen records and historical photography promises to be a valuable additional tool for determining invasion dynamics.

Prairie-pothole wetlands provide the critical habitat necessary for supporting North American migratory waterfowl populations. However, climate and land-use change threaten the sustainability of these wetland ecosystems. Very few experiments and analyses have been designed to investigate the relative impacts of climate and land-use change drivers, as well as the antagonistic or synergistic interactions among these drivers on ecosystem processes. Prairie-pothole wetland water budgets are highly dependent on atmospheric inputs and especially surface runoff, which makes them especially susceptible to changes in climate and land use. Here, we present the history of prairie-pothole climate and land-use change research and address the following research questions: 1) What are the relative effects of climate and land-use change on the sustainability of prairie-pothole wetlands? and 2) Do the effects of climate and land-use change interact differently under different climatic conditions? To address these research questions, we modeled 25 wetland basins and measured the response of the lowest wetland in the watershed to wetland drainage and climate variability. We found that during an extremely wet period (1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000) wetland drainage decreased the time at which the lowest wetland reached its spill point by four years, resulting in 10 times the amount of water spilling out of the watershed towards local stream networks. By quantifying the relative effects of both climate and land-use drivers on wetland ecosystems our findings can help managers cope with uncertainties about flooding risks and provide insight into how to manage wetlands to restore functionality.Sustainability 2019, 11, 6581 2 of 20 and biological (e.g., vegetation and aquatic macroinvertebrate communities) variables of interest in areas where vulnerable wetlands that have been well documented as a "disappearing ecosystem" [4].The Prairie Pothole Region (PPR) covers approximately 777,000 km 2 of the North American midcontinent (Figure 1). Over half of the historical wetlands in the PPR have been drained, and conversion of upland areas to crops has altered wetland functioning and the ecosystem services provided by wetlands [5]. Millions of small, glacially derived wetlands that provide critical habitat for migratory waterfowl [5] and other wetland-dependent species [6,7] occur in the PPR, making it a continentally significant region for biodiversity [8]. The wetlands of the PPR also provide additional ecosystem services such as floodwater storage, sediment reduction, water-quality improvement [9], and carbon sequestration [10]. The need to tease apart the complexity caused by interactions between climate and land-use change drivers and how they affect biodiversity, in general, has been recently established as a pressing research priority for ecosystem scientists and land managers [2]. Understanding the relative impacts of climate and land-use change on wetland hydrology is critical for developing land-management strategies...

LETTER • OPEN ACCESSGroundwater recharge in desert playas: current rates and future effects of climate change AbstractOur results from playas, which are topographic low areas situated in closed-catchments in drylands, indicated that projected climate change in Southwestern USA would have a net positive impact over runon and groundwater recharge beneath playas. Expected increased precipitation variability can cause up to a 300% increase in annual groundwater recharge beneath playas. This increase will overshadow the effect of decreased precipitation amount that could cause up to a 50% decrease in recharge beneath playas. These changes could have a significant impact on groundwater and carbon storage. These results are important given that groundwater resources in Southwestern USA continue to decline due to human consumption outpacing natural recharge of aquifers. Here, we report on groundwater recharge rates ranging from less than 1 mm to greater than 25 mm per year beneath desert playas. Playas located in larger and steeper catchments with finer-textured soils had the highest rates of recharge. Vegetation cover had no effect on recharge beneath playas. We modeled catchment runoff generation and found that the amount of runon a playa receives annually strongly correlated to the rate of groundwater recharge beneath that playa. Runon occurred during precipitation events larger than 20 mm and increased linearly with events above that threshold.

Development of the Pothole Hydrology-Linked Systems Simulator model would not have been possible but for the pioneering work of George A. Swanson (deceased), Thomas C. Winter (deceased), Donald O. Rosenberry, and James W. LaBaugh who worked together in the late 1970s and early 1980s to establish the surface-water, groundwater, and water-chemistry monitoring network at the Cottonwood Lake Study Area. We also are greatly indebted to Ned H. Euliss, Jr., who expanded the monitoring effort in 1992 to include detailed quantifications of the water-bird, amphibian, aquatic-macroinvertebrate, and plant communities at the site. We also thank Richard D. Nelson for ensuring that water chemistry sampling continued at the site during a period (1992-2002) when previous sources of funding became unavailable. We thank the many technicians, biologists, ecologists, student contractors, and volunteers who have worked tirelessly over the years to collect, enter, and maintain the rich data resources now available from the study site. We especially thank Bruce Hanson, Richard Hegvik, Stephen Lane, and Matthew Solensky for their efforts leading field crews and supervising laboratory processing of collected samples. Initial funding supporting the development of a systems model for prairie-pothole wetlands was provided by the Conservation Effects

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Alternative stable states are nontransitory states within which communities can exist.However, even highly dynamic communities can be viewed within the framework of stable-state theory if an appropriate "ecologically relevant" time scale is identified.The ecologically relevant time scale for dynamic systems needs to conform to the amount of time needed for a system's community to complete an entire cycle through its normal range of variation. For some systems, the ecologically relevant period can be relatively short (eg, tidal systems), for others it can be decadal (eg, prairie wetlands). We explore the concept of alternative stable states in unstable systems using the highly dynamic wetland ecosystems of North America's Prairie Pothole Region.The communities in these wetland ecosystems transition through multiple states in response to decadal-long climate oscillations that cyclically influence ponded-water depth, permanence, and chemistry. The perspective gained by considering dynamic systems in the context of stable-state theory allows for an increased understanding of how these systems respond to changing drivers that can push them past tipping points into alternative states. Incorporation of concepts inherent to stable-state theory has been suggested as a key scientific element upon which to base sustainable environmental management. K E Y W O R D Salternate stable states, community change, dynamic systems, ecological theory, prairiepothole wetlands, state shifts

Grasslands, and the depressional wetlands that exist throughout them, are endangered ecosystems that face both climate and land‐use change pressures. Tens of millions of dollars are invested annually to manage the existing fragments of these ecosystems to serve as critical breeding habitat for migratory birds. The North American Prairie Pothole Region (PPR) contains millions of depressional wetlands that produce between 50% and 80% of the continent’s waterfowl population. Previous modeling efforts suggested that climate change would result in a shift of suitable waterfowl breeding habitat from the central to the southeast portion of the PPR, an area where over half of the depressional wetlands have been drained. The implications of these projections suggest a massive investment in wetland restoration in the southeastern PPR would be needed to sustain waterfowl populations at harvestable levels. We revisited these modeled results indicating how future climate may impact the distribution of waterfowl‐breeding habitat using up‐to‐date climate model projections and a newly developed model for simulating prairie‐pothole wetland hydrology. We also presented changes to the number of “May ponds,” a metric used by the U.S. Fish and Wildlife Service to estimate waterfowl breeding populations and establish harvest regulations. Based on the output of 32 climate models and two emission scenarios, we found no evidence that the distribution of May ponds would shift in the future. However, our results projected a 12% decrease to 1% increase in May pond numbers when comparing the most recent climate period (1989–2018) to the end of the 21st century (2070–2099). When combined, our results suggest areas in the PPR that currently support the highest densities of intact wetland basins, and thus support the largest numbers of breeding‐duck pairs, will likely also be the places most critical to maintaining continental waterfowl populations in an uncertain future.