Assessing threats of non-native species to native freshwater biodiversity: Conservation priorities for the United States

Hydrocharis laevigata in Europe

Hydrocharis laevigata (Humb. & Bonpl. ex Willd.) Byng & Christenh. [= Limnobium laevigatum (Humb. & Bonpl. ex Willd.) Heine], Hydrocharitaceae, is a floating-leaf aquatic plant that is native to inland South America. It is an invasive species in several parts of the world. Reports of its presence in Europe have been recently published: naturalised populations occur in three locations on the Iberian Peninsula. The literature also contains records of the species in Hungary and Poland. In addition, it has been observed in Sweden, Belgium, and the Netherlands. H. laevigata is highly adaptable and can profoundly transform habitat conditions in its invasive range, causing major issues for ecosystem conservation and human activities. Until recently, H. laevigata was not to be found in natural environments in Europe. Factors explaining its spread include its use as an ornamental plant, the eutrophication of inland waters, and the effects of global warming. With a focus on Europe, this short communication provides information on the species' distribution, taxonomy, biology, habitat, and negative impacts.

Effect of freshwater on plant species diversity and interspecific associations in coastal wetlands invaded by Spartina alterniflora

Plant invasions in coastal wetlands lead to the degradation of native vegetation; the introduction of freshwater in coastal wetlands would prevent the spread of invasive plants and facilitate the restoration of native vegetation. In this study, we evaluated the effects of freshwater on plant communities in the coastal wetlands of Yancheng, China, invaded by Spartina alterniflora Loisel. Two field investigations were conducted in 2008 and 2018 before and after the introduction of freshwater (started in 2011). The characteristics of plant communities were subjected to hierarchical cluster analysis and compared using several diversity indices. In addition, differences in habitat community composition and interspecific relationships of dominant species were analyzed. The results showed that S. alterniflora reduced the overall species diversity in the region. Plant species diversity increased after freshwater was introduced into the study site when compared to the areas without freshwater introduction. The introduction of freshwater caused a shift often changes in the interspecific relationships between Suaeda salsa (L.) Pall. and other species. The intensified invasion of S. alterniflora changed the interspecific relationship of native halophytes from negative to positive. Although freshwater effectively inhibited further invasion of S. alterniflora, it also increased the risk of expansion of the glycophytes in the community. The results of this study highlight the need for early intervention for restoration of coastal wetlands, preservation of biodiversity, and management of plant resources.

Can Remote Sensing Fill the United States’ Monitoring Gap for Watershed Management?

Remote sensing has been heralded as the silver bullet in water quality modeling and watershed management, and yet a quantitative mapping of where its applicability is likely and most useful has not been undertaken so far. Here, we combine geospatial models of cloud cover as a proxy for the likelihood of acquiring remote scenes and the shortest time of travel to population centers as a proxy for accessibility to ground-truth remote sensing data for water quality monitoring and produce maps of the potential of remote sensing in watershed management in the United States. We generate several maps with different cost-payoff relationships to help stakeholders plan and incentivize remote sensing-based monitoring campaigns. Additionally, we combine these remote sensing potential maps with spatial indices of population, water demand, ecosystem services, pollution risk, and monitoring coverage deficits to identify where remote sensing likely has the greatest role to play. We find that the Southwestern United States and the Central plains regions are generally suitable for remote sensing for watershed management even under the most stringent costing projections, but that the potential for using remote sensing can extend further North and East as constraints are relaxed. We also find large areas in the Southern United States and sporadic watersheds in the Northeast and Northwest seaboards and the Midwest would likely benefit most from using remote sensing for watershed monitoring. Although developed herein for watershed decision support in the United States, our approach is readily generalizable to other environmental domains and across the world.

Quantitative conservation geography

Ongoing biodiversity loss represents the erosion of intrinsic value of living nature, reduces the contributions nature provides to people, and undermines efforts to move towards sustainability. We propose the recognition of quantitative conservation geography as a subfield of conservation science that studies where, when, and what conservation actions could be implemented in order to mitigate threats and promote sustainable people-nature interactions. We outline relevant methods and data needed in quantitative conservation geography. We also discuss the importance of filling information gaps, for example by using emerging technologies and digital data sources, for the further advancement of this subfield. Quantitative conservation geography can help inform the implementation of national and international conservation actions and policy to help stem the global biodiversity crisis.

Non-native Asian swamp eel, Monopterus albus/javanensis (Zuiew, 1973/Lacepede, 1800), responses to low temperatures

Asian swamp eel, Monopterus albus/javanensis [Zuiew, 1973/Lacepede 1800], has been established in the southeastern USA since at least 1994, yet little is known about its ability to survive low winter temperatures. We use standard thermal methodologies to quantify low temperature responses and provide a detailed description of swamp eel reactions to cold temperatures. When exposed to chronic temperature decreases of 1.0 °C day^-1, swamp eel ceased foraging at 15.0 °C, markedly diminished movements below 11.0 °C, and became incapacitated near 9.6 °C. During critical thermal minima trials, swamp eel exposed to acute temperature drops (0.25 °C min^-1) tolerated temperatures as low as 6.2 °C. Swamp eel exhibited a moderate cold acclimation response, gaining 0.23 °C in cold tolerance for every 1 °C drop in acclimation temperature. Progressive time-series critical thermal minimum temperatures (CTmin) estimates for eel acclimated to 20.5 °C followed by an acute temperature decrease to 16.0 °C, revealed that cold acclimation may occur in only 8 days. Fringe populations of swamp eel in their native range periodically experience colder winter temperatures, which may explain the ability of introduced populations to survive winter cold fronts in Florida. Understanding Asian swamp eel acute and chronic thermal limits may be useful in assessing dispersal risk and range expansion in the southeastern USA.

Automatic Extraction and Filtering of OpenStreetMap Data to Generate Training Datasets for Land Use Land Cover Classification

This paper tests an automated methodology for generating training data from OpenStreetMap (OSM) to classify Sentinel-2 imagery into Land Use/Land Cover (LULC) classes. Different sets of training data were generated and used as inputs for the image classification. Firstly, OSM data was converted into LULC maps using the OSM2LULC_4T software package. The Random Forest classifier was then trained to classify a time-series of Sentinel-2 imagery into 8 LULC classes with samples extracted from: (1) The LULC maps produced by OSM2LULC_4T (TD0); (2) the TD1 dataset, obtained after removing mixed pixels from TD0; (3) the TD2 dataset, obtained by filtering TD1 using radiometric indices. The classification results were generalized using a majority filter and hybrid maps were created by merging the classification results with the OSM2LULC outputs. The accuracy of all generated maps was assessed using the 2018 official “Carta de Ocupação do Solo” (COS). The methodology was applied to two study areas with different characteristics. The results show that in some cases the filtering procedures improve the training data and the classification results. This automated methodology allowed the production of maps with overall accuracy between 55% and 78% greater than that of COS, even though the used nomenclature includes classes that can be easily confused by the classifiers.

Effects of Nonnative Fishes on Commercial Seine Fisheries: Evidence from a Long-Term Data Set

Dozens of introduced exotic freshwater fish species inhabit the state of Florida. These nonnative fishes interact with freshwater commercial fisheries in a variety of ways, influencing catch abundance, composition, and revenue. Using a 22-year data set collected from a commercial haul seine fishery, we aimed to explore the dynamics of yield and revenue in relation to nonnative fishes, with emphasis on the suckermouth armored catfishes (Pterygoplichthys spp.). Using profit index metrics and the inverse Simpson’s diversity index, we found that non-native tilapia (Oreochromis spp.) and brown hoplo (Hoplosternum littorale) provided economic benefits while suckermouth armored catfishes seemed to disrupt catch consistency and lower profit index values. To reduce the negative impacts of the suckermouth armored catfishes and subsequently exert pressure on their population, we suggest marketing these edible fishes for human and/or animal consumption.