Becky Tang is the recipient of a NSF-GRFP 2020 award, announcement just in, details to follow…
ESA Selects 2020 Katherine S. McCarter Graduate Student Policy Award Recipients
The Ecological Society of America (ESA) is honored to announce this year’s Katherine S. McCarter Graduate Student Policy Award (GSPA) recipients. This award provides graduate students with the opportunity to receive policy and communication training in Washington, DC before they meet lawmakers.
ESA selected twelve students to receive the award: Tiffany L. Betras (University of Pittsburgh), Callie R. Chappell(Stanford University), Claire E. Couch (Oregon State University), Ayo Andra J. Deas (The Graduate Center, City University of New York), Ed Higgins (University of Oklahoma), Renata Poulton Kamakura (Duke University), Alexander K. Killion (University of Michigan), Mayda Nathan (University of Maryland), Vasavi Prakash (Auburn University), Natali R. Ramirez-Bullon (Florida State University), Bradley A. Strickland (Florida International University) and Harrison R. Watson (Princeton University).
here are abstracts submitted by the lab to the 2020 annual meeting of the Ecological Society of America;
Capturing emergent interactions that govern food web dynamics with climate change
Background/Question/Methods Observational studies have not yet shown that environmental variables can explain pervasive non-linear patterns of species abundance, because those patterns could result from (indirect) interactions with other species (e.g., competition), and models only estimate direct responses. We developed a bio-physical approach to quantify the environment-species interactions (ESI) that govern community change. By embedding dynamic ESI within a time-series framework that admits data for species gathered on different scales, we quantify responses that are induced indirectly through ESI. A hierarchical framework provides probabilistic uncertainty in parameters, model specification, and data. Simulation demonstrates that effects of environment on movement, population growth, and species interactions are needed for accurate interpretation. Applications include published data sets on lake food webs and the breeding bird survey (BBS). For NEON ground beetles, small mammals, and bird data we integrate remote sensing, including lidar and hyperspectral data from the airborne observation platform.
Results/Conclusions Analytical analysis demonstrates how non-linear responses arise even when all direct species responses to environment are linear. Applications to experimental lakes and BBS yield contrasting estimates of ESI. In closed lakes, interactions involving phytoplankton and their zooplankton grazers play a large role. By contrast, ESI are weak in BBS, as expected where year-to-year movement degrades the link between local population growth and previous species abundances. In both cases, non-linear responses are induced by interactions between species. Stability analysis shows stability in the closed-system lakes and instability in BBS. NEON analysis is underway to evaluate how canopy condition and habitat structure mediate food web interactions. The probabilistic framework also has direct application to conservation planning that must weigh risk assessments for entire habitats and communities against competing interests.
Is citizen science a reliable source of big data? Identifying biases in eBird records
Background/Question/Methods Understanding how biodiversity is changing requires a capacity to combine information from different sources. Opportunistic citizen science observations are an increasingly important source of data for continent-scale studies of global change and biodiversity. eBird is one of the most successful and popular citizen scientist projects, with over 100 million birds recorded each year by users with varying degrees of experience and species identification skills. By contrast, the Breeding Bird Survey (BBS) is systematic, completed annually at the same times and locations, and is conducted by trained personnel. To determine if these data sources could be integrated, we quantified the differences between them. We compared eBird observations to the more rigorously collected BBS records for 300 species by aggregating eBird checklists spatially near (within 40 km of) BBS routes and at the same time of year. First, we fitted the bird count data from both sources with environmental covariates using a Generalized Joint Attribute Model (GJAM), with data source as a factor covariate and observation effort as observation minutes. The fitted coefficients for the source factor are hereafter termed the “eBird effect”. We then examined the difference between counts per effort from eBird records and from BBS records at each site (“residuals”), and determined the relationship between residuals and observation effort. We used species trait data to determine whether reporting biases might be anticipated from species traits.
Results/Conclusions We found that overall, eBird users underreport most species relative to BBS, but increased observation effort minimizes these effects. Of the 132 species with eBird effect estimates whose credible intervals did not cross zero, 91 (69%) were negative. These estimates were negatively correlated with commonness (R = -0.183), indicating that common species are most underreported. We also found that for 204 species (68%) the differences between the two data sources decreased with increased observation effort. This pattern was also influenced by commonness: there was a positive correlation between commonness and residual-effort relationship (R = 0.162), meaning that for more common species, increased effort of the eBird observation actually increased the difference between the two data sources. Overall, these results indicate that eBird data contain biases, these biases vary by species commonness, and some of these biases can be overcome with increased effort. Because eBird data are often used to evaluate species populations and develop management strategies, particularly for rare species, understanding these biases is crucial.
Understanding the diverse responses of South African savanna communities to climate change
Background/Question/Methods The Kruger National Park (KNP) in northeast South Africa harbors a unique assemblage of Pleistocene megafauna, increasingly threatened by protracted drought. Managers are concerned that climate change has destabilized this diverse food web by reorganizing competition for surface water resources and shifting ranges. Such destabilization could appear as responses to vegetation and rainfall variation. In particular, locally rare antelope populations (tsessebe Damaliscus lunatus, eland Taurotragus oryx, sable Hippotragus niger, roan Hippotragus equinus) have plummeted over the past six decades, bringing about a decline in the biodiversity that is a cornerstone of tourism and ecosystem resilience. Management of a diverse, destabilized community necessitates an understanding of how species individually and collectively respond to their environment. Such communities susceptible to disturbance are a challenge for traditional species distribution models (SDMs), whose static data lose much of the information present in increasingly available long-term datasets. We utilize decades of census, vegetation, and climate data from the KNP in a dynamic generalized joint attribute model, GJAMTime, extending a traditional Lotka-Volterra framework to include density-independent growth and interspecific density dependence. Our assessment of how changing vegetation, surface water, and biotic interactions have influenced biodiversity in the KNP provides a framework for future adaptive management decisions.
Results/Conclusions Outputs consistent with prior knowledge of biotic and environmental interactions confirm that our model works well in predicting species distribution and behavior. Our model estimated similar responses to environmental variables for species known to respond similarly (i.e. blue wildebeest Connochaetes taurinus and plains zebra Equus quagga). The model attributes little variation in species abundance to movement, which is consistent with almost-full fencing around the park. We found that rare antelope distributions are mostly attributable to density-independent growth. Roan and eland have negative responses to temporal anomalies in grass biomass, and roan and tsessebe respond positively to nutrient-rich clay soils. Sable, however, responded positively to vegetation anomalies and negatively to clays, which suggests an affinity for conditions not shared by the other three. We find that climate change does affect this savanna community, but that consequences for rare antelope are not uniform, indicating a need for more targeted, adaptive management practices.
North American tree migration paced by fecundity and recruitment through contrasting mechanisms east and west
Background/Question/Methods Global forest diebacks are the beginnings of change that will be controlled by tree migration, which combines two uncertain processes, tree fecundity and recruitment. Knowledge of how, and how fast, tree migration can proceed is critical for adaptive management of forest resources and conservation efforts. The initial stage of seed production is erratic and poorly observed, with most studies limited to few trees of few species on few sites. At the next stage, tree recruitment is typically too sporadic to characterize at landscape scales. Neither seed production nor seedling recruitment have been quantified or linked to climate and habitat variables at scales needed to evaluate the changes happening now or to anticipate the diversity and structure of 21st century forests. As part of the masting inference and forecasting (MASTIF) project, we synthesized continental-scale data for tree fecundity gathered over the last half century and combined it with forest inventories to connect adult trees (basal area) to i) fecundity (seeds per basal area) and ii) recruitment (recruits per seed). A dynamic model fitted to > 107 tree years of fecundity data provided estimates tree-by-year fecundity. A predictive distribution for the continent combines the fitted model with > 105 trees from Forest Inventory Analysis (FIA), Canadian National Forest Inventory (CNFI) and the National Ecological Observatory Network (NEON).
Results/Conclusions Results show continent-wide tree migration as a balance between regional shifts in fecundity that can diverge from conditions that favour establishment, with clear differences in eastern and western North America. In moist eastern states, the geographic centers for fecundity are most commonly displaced south of tree basal area for the same species. This relationship would be expected if optimal conditions for seed production lie to the south of optimal conditions for growth and survival, despite potential benefits of warming poleward. In the dry west and north-central, fecundity is for most species displaced northwest of tree basal area, as would be expected if the high-rainfall NW is predisposed to lead migration as the continent warms. The east-west contrast diminishes at the transition from fecundity to recruits per seed, which tends to be shifted north in both regions. The net continent-wide migration by contrasting east-west controls highlight interactions, with fecundity primed to lead tree migration in the west, and fecundity slowing progress in the east. The possibility of fecundity limitation offers one explanation for migration lag in species expected to track climate warming by expanding poleward.
Interactions that control the pace of forest change in North America
Background/Question/Methods: Forests can continue to deliver ecosystem services if tree fecundity keeps pace with 21st century climate change. Not only is fecundity unknown at the continental scale, but so too is its rate of change (ROC). Is seed production responding to climate change and, if so, how? At least two forces could be controlling trends in forest regeneration and the capacity to migrate, i) climate change, and ii) geographic variation in stand growth and structure. Effective management will depend on an understanding of both effects. For example, warming during vulnerable spring months might increase reproductive success. If fecundity is limited by thermal energy that coincides with moisture availability, then warming might benefit reproduction only in regions where moisture remains abundant. At the same time, indirect effects could dominate the response if changing growth moves stands into more or less fecund size classes. We combined an unprecedented synthesis of North American fecundity data from the masting inference and forecasting (MASTIF) collaboration with a novel dynamic bio-physical model to infer continental ROC in fecundity. The biophysical model captures the direct and indirect effects of climate change, including the interactions between them (e.g., size differences matter most in dry climates, or, moisture limitation is most important for small trees).
Results/Conclusions: Fecundity, discussed here as seeds/ha/yr, is highest in the midwest (MW) and west (W) owing to high seeds per basal area in the MW and high basal area of trees in the W. However, fecundity is increasing throughout most of the continent, with highest ROC in the north (N) and northwest (NW). Exceptions include parts of the south (S) and southwest (SW). The full effect of climate change is accelerating ROC in the MW and SW both directly and through effects on growth. Two processes are offsetting a positive effect of warming springs. First, a positive effect on growth moves stands into larger, less fecund size classes in western Canada, the Rockies, and much of the East. However, positive effects on growth do not transfer to increased ROC in much of the W and NE. Despite positive ROC throughout most of the continent, climate change is reducing ROC in the East and NW. Taken together, the full effect of climate change on ROC is primarily positive, despite negative indirect effects. We discuss the implications of species-level differences for migration potential and food web dynamics.
Dear Dr. Clark:
Congratulations on your most cited article in Global Change Biology (GCB)!
Your paper, The impacts of increasing drought on forest dynamics, structure, and biodiversity, was one of the top 25 most cited articles in 2019.
Although a relatively young journal, our Impact Factor has been growing steadily – our ISI Impact Factor was 8.88 in 2018 (ISI Journal Citation Reports). GCB’s 2018 ISI ranking is first in Biodiversity Conservation, fifth in Environmental Sciences, sixth in Ecology. This ranking is all the more impressive given that, unlike our competitors, we carry very few review articles- which tend to skew Impact Factors upwards.
Thank you once again for your contribution to GCB. We hope you will continue to consider GCB as an outlet for your best work and encourage others to do likewise.
With best wishes,
Steve Long, Chief Editor and on behalf of the Editors of GCB
In today’s Popular Science, Ellen Airhart discusses the emerging disaster in Australia, as record heat and drought lead to explosive fires, while precluding the controlled burns needed for effective fuel management. Read more…
Renata has been awarded support for the first ever Graduate Leaders in Socio-Environmental (S-E) Synthesis workshop at the National Socio-Environmental Synthesis Center (SESYNC), which takes place in January 2020, read more…
Lareats for Make Our Planet Great Again (MOPGA) met with President Macron and government officials yesterday in Paris to discuss science and policy. Several of us were asked to address specific topics of concern, in my case, policy priorities that address biodiversity threats. Below are these thoughts:
Reducing the CO2 concentration of the atmosphere should be the highest policy priority. Appreciating the urgency doesn’t require a long-term perspective. The climate five years from now will not look like the climate of five years ago. Those who feel unscathed by recent extremes do not have long to wait. Each year we set temperature records. Many of this year’s records will fall next year. And again the year after that. We are not experiencing a ‘new normal’, but a trend with no visible endpoint. All other policy actions that could be taken now won’t matter if we fail to curb climate change. Efforts to save specific habitats and species will be overwhelmed by the direct, physiological impacts of heat and drought stress. I’ll start by saying why I believe that warming is the biggest crisis facing biodiversity. I’ll follow with a few words on what we can do about it.
Biodiversity faces many threats. Why do greenhouse gas emissions rise to the top of my policy concern for saving species? First, it’s important to put in perspective what we are learning from research. Much of global change science has focused on benchmarks that are used to compare models. This practice started as the ‘doubled CO2’ scenario. Today, model comparisons focus on a small number of emissions scenarios for specific dates in the future, e.g., the year 2050. Benchmarks often take the form of maps comparing where a species occurs today and where it could potentially occur under a specific scenario.
These benchmarks have substantial scientific value, but they are not the best way to think about the challenges faced by species. The locations of suitable habitats have become moving targets. As the ‘suitable climate’ for a species moves across continents, it traverses unsuitable habitat. Species that can move are doing so, but each at its own pace and in different ways. Species that survive will be those that track these transient opportunities into the future. Suitable habitats for many will disappear or just become too unreliable. Species that outrun their natural enemies may benefit in the short term. But they’re not necessarily the species we’d like to see more of. Others are finding that suitable climates are no longer in the places where they can find food.
The prediction map for a species’ future ‘suitable climate’ can be diversionary; this is a race with climate change, it’s on now, and it’s not guided by benchmarks used to compare models. Without meaningful change in policy, this race has no finish line. We have no scientific foundation for the notion of a future ‘stable climate’. Thus far, we only have goals for reducing emissions, such as the Paris agreements that we’ve been unable to meet. The reorganization of biodiversity that is in progress now doesn’t have much to do with benchmarks. We cannot ‘prepare’ for a world that looks like any of these maps.
Ecologists feel acutely the loss of a single species. Today, we are talking about the loss of entire habitats, communities, and ecosystems. The cascading impacts on disease spread and food security are unknown. For me, the top policy priority for saving species is reduction in greenhouse gas emissions.
Both the looming crisis and what we can do about it have much to do with leadership. Our individual actions to use recyclables and alternative energy sources contribute to a collective sense of enfranchisement in the future. This ethic is critical. But these individual actions should not be mistaken for solutions to the current crisis. That has to come from leadership at the policy level.
The most important action for each of us can focus on the support of leaders who can make a difference. The leadership vacuum created by the withdraw of the US administration from climate negotiation has to be filled by others. We need change in the US. As you Mr. President are well aware, leadership in the future will be international. Those leaders will have a clear understanding that reducing greenhouse gas concentrations must happen now. We see your role as placing climate change at the top of policy goals. Ours is to push for leadership at all levels of government.
Thanks for the opportunity to contribute our scientific understanding to this most important of human challenges.
The level of climate awareness and activism in Europe is unlike anything we’ve seen in the US. Yesterday’s march in Madrid came together quickly, just days after the venue for the UN climate talks moved here from Santiago Chile. We joined the massive crowd at Canovas Del Castillo, then peeled off to observe from atop the Palacio de Cibeles. For two hours the protest streamed north, estimated by organizers at 500,000. Local and international coverage highlighted the concerns that talks result in meaningful change.
Lane’s proposal “Nature and People” for the Spring University Program in Ecology (UPE) symposium has been funded, details to follow.
Our new project on FORcasting BIodiversity Change (FORBIC), part of France’s Make Our Planet Great Again (MOPGA) is featured in the Christian Science Monitor, here.
The impacts of drought can be devastating and long-lasting, from the loss of valuable crops and trees to increased wildfire risk. Droughts are difficult to predict since they are caused by the interaction of precipitation, temperature, and topography. A team of researchers from Coweeta LTER, led by Dr. Bijan Seyednasrollah, has developed a drought monitoring method that relies on remotely sensed data, operates in near real-time, and correlates very well with traditional methods.. [read more]
The Nuñez years draw to a close with the defense of a fine thesis, papers coming out, and all those post-doc interviews. Stay in contact!
Awards ceremony at the von Humboldt Foundation last week with Christian Pape. Also honored from Duke was Anne Yoder, Biology Department. more here…
The lives of more than two billion people are affected by drought and could benefit from monitoring plant stress in real time. The extensive data collection and in-situ calibration that would be needed for continental scale estimates are difficult to implement in ways that could provide assessments of current conditions.
We used a simple relationship between the atmosphere and plants to extract real-time plant stress. Ordinarily, plant canopies are cooled by leaf water loss through stomata. These small pores in leaf surfaces lose water as they admit CO2 from the atmosphere. This evaporative cooling limits the canopy-atmosphere temperature differential, explaining why summertime mid-day temperatures within forest canopies are cooler than in cities. This cooling mechanism is driven by water uptake from the soil and remains effective until plants are moisture-limited, leading to stomatal closure, and surface heating. This simple relationship led us to speculate that the canopy-atmosphere differential, or “thermal stress”, could provide a real-time index of moisture limitation and of plant water consumption in warm seasons.
Combining the measurements from thousands of land-based weather stations and satellite-based ‘skin temperature’ of the canopy, Seyednasrollah et al. found thermal stress to be a reliable indicator of drought-induced water stress at the continental scale. Comparisons with land-based measurements showed that a 1 °C change in thermal stress is comparable to 1 to 1.2 mm of daily evapotranspiration, depending on site and climate conditions. Read more here.
Clark contributed to the Forests chapter:
Earth’s climate is now changing faster than at any point in the history of modern civilization, primarily as a result of human activities. The impacts of global climate change are already being felt in the United States and are projected to intensify in the future—but the severity of future impacts will depend largely on actions taken to reduce greenhouse gas emissions and to adapt to the changes that will occur… [read the report]
The amount of water available to a tree determines its susceptibility to drought. It has been one of the big unknowns in predicting responses to climate change. Here we show that it can be measured:
We apply this model to multiple seasonal droughts with tree transpiration measurements to demonstrate how species and size differences modulate moisture availability across landscapes. The depletion of individual moisture reservoirs can be tracked over the course of droughts and linked to biomass growth and reproductive output. This mass balance approach can predict individual moisture deficit, tree demographic performance, and drought vulnerability throughout forest stands based on measurements from a sample of trees, more here
A warming climate is changing the pace of spring green-up. Using remote sensing and a new approach that quantifies the rate of green-up, Seyednasrollah et al show that green-up is fast in the mountains and relatively insensitive to temperature anomalies, while slow development in warm, coastal forests can respond to temperature swings. Confirming experimental evidence, this study shows that spring is compressed in cold climates, delayed in onset but then rapidly progressing to full leaf expansion. Conversely, mountainous forest green-up is more susceptible to intensifying drought and moisture deficit, while coastal areas are relatively resilient. Canopy thermal stress slows leaf development following dry years, but accelerates it following wet years. The study is published in Remote Sensing of Environment.
Arbuscular mycorrhizal (AM) fungi in the soil may influence tropical tree dynamics and forest succession. The mechanisms are poorly understood, because the functional characteristics and abundances of tree species and AM fungi are likely to be codependent. We used generalized joint attribute modeling to evaluate if AM fungi are associated with three forest community metrics for a sub-tropical montane forest in Puerto Rico. (read more …)