Abstract: Global change stressors such as drought and plant invasion can affect ecosystem structure and function via mediation of resource availability and plant competition outcomes. Yet, it remains uncertain how native plants respond to drought stress that co-occurs with potentially novel resource conditions created by a nonnative invader. Further, there is likely to be temporal variation in competition outcomes between native and nonnative plant species depending on which resources are most limiting at a given time. Interacting stressors coupled with temporal variation make it difficult to predict how global change will impact native plant communities. To address this knowledge gap, we conducted a 5-yr factorial field experiment to quantify how simulated drought, plant invasion (by cogongrass, Imperata cylindrica), and these stressors combined, affected resource availability (soil moisture and light) and competition dynamics between the invader and native longleaf pine (Pinus palustris), a foundation species in southeast U.S. forests. Drought and invasion mediated the survival and performance of pine seedlings in temporally dynamic and unexpected ways. Drought and invasion alone each significantly reduced pine seedling survival. However, when the stressors occurred together, the invader offset drought stress for pine seedlings by maintaining high levels of soil moisture, humidity, and shade compared to uninvaded vegetation. This facilitative effect was pronounced for 2 yr, yet shifted to strong competitive exclusion as the invasion progressed and the limiting resource switched from soil moisture to light. After 3 yr, pine tree survival was low except for pines growing with uninvaded vegetation under ambient precipitation conditions. After 5 yr, pines experiencing a single stressor were taller and had greater height to diameter ratios than pines under no stress or both stressors. This outcome revealed a filtering effect where poorly performing trees were culled under stressful conditions, especially when pines were growing with the invader. Together, these results demonstrate that although drought and invasion suppressed a foundation tree species, the invader temporarily moderated stressful drought conditions, and at least some trees were able to survive despite increasingly strong competition. Such unpredictable effects of interacting global change stressors on native plant species highlight the need for additional long-term studies.

Abstract: Of the approximately 50,000 nonnative species that have been introduced into the United States, nearly 4,600 of them are classified as harmful invasive species (Pimentel et al., 2000; Corn et al., 2002). These organisms have caused major economic and environmental damages to the tune of $120 billion per year (Pimentel, Zuniga, and Robinson, 2005). Invasive species have also been found to negatively impact human well-being (Jones, 2017) and to induce trophic cascades (Walsh, Carpenter, and Vander Zanden, 2016). The annual toll inflicted by invasive species to U.S. agriculture is significant: Pest insects cause an estimated $13 billion in crop losses on top of the $1.2 billion farmers spend in insecticides, while weeds cause an estimated reduction of 12% in crop yields ($33 billion in production losses) despite $3 billion spent on herbicides each year (Pimentel et al., 2000). Similarly, invasive forest pests cause nearly $5 billion in damages and losses throughout the United States, including $2.25 billion in costs to governments, $2.55 billion in costs to homeowners, and $152 million in losses to timber producers (Aukema et al., 2011). In the past 40 years, biological invaders and the risk associated with them have increased mainly due to rapid human population growth and mobility coupled with radical alteration of ecosystems across the globe. In addition, more goods and materials are being traded between nations than ever before, creating opportunities for unintentional introductions (Perrings et al., 2002; Evans, 2003; Alvarez, 2016). Recent analyses on invasion threats indicate that the level of damages to agriculture worldwide is likely to increase, with major food-producing nations such as the United States, Canada, China, Argentina, Australia, and South Africa among the most threatened nations (Paini et al., 2016). While government agencies have developed guidance documents with specific recommendations for early detection and rapid response (National Invasive Species Council, 2016; U.S. Department of the Interior, 2016) and some international agreements mention invasive species (Lodge et al., 2016), there are no clear science-based national policies to deal with invasive species in the United States (Mhina et al., 2016). Instead, response efforts have been established on a case-by-case basis, and policy makers and stakeholders play a big role in deciding which invasions are targeted for control or eradication and when those efforts are to take place. Here we offer evidence that the economic costs associated with invasive species is in large part determined by the response time between arrival of a pest and the beginning of eradication or control efforts. To make our case, we first discuss the three phases of a biological invasion and the main strategies—in terms of response time—that policy makers have followed to deal with the threat. We also present a review of representative biological invasions that have affected Florida’s agriculture industry, categorized by the invasion phase in which eradication efforts were implemented. Finally, we discuss policy implications and recommendations.

Abstract: Vibrio vulnificus has been identified as one of the main causative agents of foodborne disease associated with shellfish consumption. Infections of V. vulnificus increase during the summer months due to higher densities of the bacteria in warmer water and inappropriate handling of shellfish. In Florida, the daily harvest period is regulated to control the length of time between shellfish harvest and processing, and this harvest period has been recently reduced during the summer months to decrease the risk of foodborne disease. Adoption of this public health policy can affect the profitability and economic sustainability of wild oyster harvesters, especially in resource-dependent coastal communities. This study develops a dynamic and stochastic bioeconomic model to assess the impact of this policy on fishers’ harvest and revenues, and weighs that impact against the policy’s potential public health benefits. Our results show that fishers will experience reduced harvests early in the season due to the shorter harvest hours, but this initial loss is partially recouped later in the season as harvests remain high for longer than they would have if the policy were not in place. This study highlights the relationship between food safety interventions and management of fishery resources, and provides a comprehensive framework for evaluating the costs and benefits associated with such interventions.

Abstract: Wheat grain protein concentration is an important determinant of wheat quality for human nutrition that is often overlooked in efforts to improve crop production. We tested and applied a 32‐multi‐model ensemble to simulate global wheat yield and quality in a changing climate. Potential benefits of elevated atmospheric CO2 concentration by 2050 on global wheat grain and protein yield are likely to be negated by impacts from rising temperature and changes in rainfall, but with considerable disparities between regions. Grain and protein yields are expected to be lower and more variable in most low‐rainfall regions, with nitrogen availability limiting growth stimulus from elevated CO2. Introducing genotypes adapted to warmer temperatures (and also considering changes in CO2 and rainfall) could boost global wheat yield by 7% and protein yield by 2%, but grain protein concentration would be reduced by −1.1 percentage points, representing a relative change of −8.6%. Climate change adaptations that benefit grain yield are not always positive for grain quality, putting additional pressure on global wheat production.

Abstract: The objective of this study was to evaluate relationships between local factors (beach geomorphology and management) and regional factors (infrastructure improvements and temperature changes) against levels of fecal indicator bacteria (FIB) at recreational beaches. Data were evaluated for 17 beaches located in Monroe County, Florida (Florida Keys), USA, including an assessment of sanitary infrastructure improvements using equivalent dwelling unit (EDU) connections. Results show that elevated FIB levels were associated with beach geomorphologies characterized by impeded flow and by beaches with lax management policies. The decrease in EDUs not connected coincided with a decrease in the fraction of days when bacteria levels were out of compliance. Multivariate factor analysis also identified beach management practices (presence of homeless and concession stands) as being associated with elevated FIB. Overall, results suggest that communities can utilize beach management strategies and infrastructure improvements to overcome the negative water quality impacts anticipated with climate change.

Abstract: Karenia brevis is a marine dinoflagellate commonly found in the Gulf of Mexico and important both ecologically and economically due to its production of the neurotoxin brevetoxin, which can cause respiratory illness in humans and widespread death of marine animals. K. brevis strains have previously shown to be sensitive to changes in CO2, both in terms of growth as well as toxin production. Our study aimed to understand this sensitivity by measuring underlying mechanisms, such as photosynthesis, carbon acquisition, and photophysiology. K. brevis (CCFWC-126) did not show a significant response in growth, cellular composition of carbon and nitrogen, nor in photosynthetic rates between pCO2 concentrations of 150, 400, or 780 µatm. However, a strong response in its acquisition of inorganic carbon was found. Half saturation values for CO2 increased from 1.5 to 3.3 µM, inorganic carbon preference switched from HCO- to CO2 (14-56% CO2 usage), and external carbonic anhydrase activity was downregulated by 23% when comparing low and high pCO2. We conclude that K. brevis must employ an efficient and regulated CO2 concentrating mechanism (CCM) to maintain constant carbon fixation and growth across pCO2 levels. No statistically significant correlation between CO2 and brevetoxin content was found, yet a positive trend with enhanced pCO2 was detected. This study is the first explaining how this socioeconomically important species is able to efficiently supply inorganic carbon for photosynthesis, which can potentially prolong bloom situations. This study also highlights that elevated CO2 concentrations, as projected for a future ocean, can affect underlying physiological processes of K. brevis, some of which could lead to increases in cellular brevetoxin production and therefore increased impacts on coastal ecosystems and economies.

Abstract: As climate change continues, sea turtle nests will be increasingly exposed to elevated incubation temperatures. Higher incubation temperatures influence many aspects of sea turtle development including sex determination and incubation length, but also survival. If temperatures in the nest increase above a thermal tolerance limit, then embryonic mortality may increase. The purpose of this research was to determine if there are differences in vulnerability to elevated temperatures across different stages of embryonic development and between loggerhead (Caretta caretta) and green (Chelonia mydas) sea turtles. Temperature dataloggers recorded nest temperature in the approximate center of loggerhead and green nests laid on the Boca Raton, Florida beach during the 2016 and 2017 nesting seasons. All unhatched eggs were collected from these nests following hatchling emergence. The eggs were dissected and the developmental stage at embryonic death was determined. The point of embryonic death was compared to the nest temperatures during that stage of the incubation period to determine if death corresponded to specific periods of elevated temperatures. Elevated nest temperatures increased embryonic mortality, but no developmental stage had higher mortality rates when exposed to any specific elevated temperatures compared to embryos that had not been exposed to that temperature. The most significant relationship was between mortality and the percent of time embryos were exposed to temperatures above 34 degrees C. This resulted in greater mortality of more developed embryos, as those embryos had a longer cumulative exposure to elevated temperatures. Loggerhead turtles exhibited higher rates of mortality compared to green turtles for almost all temperature exposure periods above 34 degrees C. Although few green nests reached 34 degrees C, green sea turtle embryos in south Florida may also have a higher thermal tolerance than loggerheads. Due to the increased embryonic mortality, and therefore, decreased hatching success, future management strategies may need to protect sea turtle nests from extended periods at elevated temperatures.

Abstract: Here we summarize the motivation and issues surrounding the responses of ice sheets and sea level to past climate warming as part of the PALeo constraints on SEA level rise (PALSEA) working group. Papers in this special issue of Quaternary Science Reviews focus on the timescale of glaciations during the late Pliocene, the magnitude of ice-sheet fluctuations and volume leading up to and during the last glacial maximum, the timing and persistence of ice-sheet impacts on deglacial and future relative sea-level change, and relative sea-level change during peak interglacial climate. A more dynamic cryosphere is noted under both late Pliocene and last glacial cycle climate conditions, while relative sea-level changes during the last deglaciation appear to correspond closely with individual ice-sheet deglaciation. Lastly, relative sea-level change during peak interglacial conditions may have fluctuated by as much as a meter, although the sources of such variability (Greenland, Antarctica or elsewhere) remain elusive. (C) 2019 Elsevier Ltd. All rights reserved.

Abstract: Global mean sea level is an integral of changes occurring in the climate system in response to unforced climate variability as well as natural and anthropogenic forcing factors. Its temporal evolution allows changes (e.g.,acceleration) to be detected in one or more components. Study of the sea-level budget provides constraints on missing or poorly known contributions, such as the unsurveyed deep ocean or the still uncertain land water component. In the context of the World Climate Research Programme Grand Challenge entitled "Regional Sea Level and Coastal Impacts", an international effort involving the sea-level community worldwide has been recently initiated with the objective of assessing the various datasets used to estimate components of the sea-level budget during the altimetry era (1993 to present). These datasets are based on the combination of a broad range of space-based and in situ observations, model estimates, and algorithms. Evaluating their quality, quantifying uncertainties and identifying sources of discrepancies between component estimates is extremely useful for various applications in climate research. This effort involves several tens of scientists from about 50 research teams/institutions worldwide (www.wcrp-climate.org/grand-challenges/gc-sea-level, last access: 22 August 2018). The results presented in this paper are a synthesis of the first assessment performed during 2017-2018. We present estimates of the altimetry-based global mean sea level (average rate of 3.1 +/- 0.3mm yr(-1) and acceleration of 0.1 mm yr(-2) over 1993-present), as well as of the different components of the sea-level budget (http://doi.org/10.17882/54854, last access: 22 August 2018). We further examine closure of the sea-level budget, comparing the observed global mean sea level with the sum of components. Ocean thermal expansion, glaciers, Greenland and Antarctica contribute 42%, 21%, 15% and 8% to the global mean sea level over the 1993-present period. We also study the sea-level budget over 2005-present, using GRACE-based ocean mass estimates instead of the sum of individual mass components. Our results demonstrate that the global mean sea level can be closed to within 0.3 mm yr(-1) (1 sigma). Substantial uncertainty remains for the land water storage component, as shown when examining individual mass contributions to sea level.

Abstract: Irrigation improvement has been identified as an important adaptation strategy for the food and water security under climate change. Ecological and economic feasibility analysis of irrigation improvement projects is of vital importance to ensure the high investment efficiency and the sustainability of irrigation development. This study integrated emergy, economic and sensitivity analysis methods into a combined analysis. A case study on a small-scale irrigation project in plain areas of Jiangsu Province in China illustrated the methodology. The results indicated that different calculation results were obtained by using emergy and economic analysis methods, respectively. The conventional monetary based analysis method could underestimate or overestimate the assessment indicators. Emergy as an eco-centric method could neglect the economic utility, human preference and demand. Economic analysis and emergy accounting as the complementary valuation methods should be jointly used to provide better insights into the environmental and economic effects of irrigation improvement projects.