Browsing by Author "Calle, Leonardo"

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How do we ensure the future of our discipline is vibrant? Student reflections on careers and culture of ecology
(2018-02) Hansen, Winslow D.; Scholl, Joshua P.; Sorensen, Amanda E.; Fisher, Kelsey E.; Klassen, Jessica A.; Calle, Leonardo; Kandlikar, Gaurav S.; Kortessis, Nicholas; Kucera, Dion C.; Marias, Danielle E.; Narango, Desiree L.; O'Keeffe, Kayleigh; Recart, Wilnelia; Ridolfi, Elizabeth; Shea, Monika E.
Ecology must attract and retain diverse talented people to produce innovative research and relevant solutions to 21st-century environmental problems. Careers and culture form the foundation of scientific advancement, and substantial progress has been made over recent decades in both realms. Yet, important challenges persist in expanding career paths, inclusion of underrepresented groups, and communication with the public. The ESA Student Section organized a horizon scanning exercise to address the following goals: (1) to identify challenges that 21st-century ecologists contend with or expect to contend with in careers and outreach to society, (2) to anticipate opportunities to help ecologists meet challenges, and (3) to identify concrete steps that could be taken by individual laboratories, institutions, and the ESA to foster progress. In spring 2016, the ESA Student Section solicited input from student members and organized a working group to assess the state of the discipline and to envision how we might cultivate a more inclusive and effective community. We identified three major challenges. First, PhDs are produced faster than academic positions become available and disconnects between academia and other sectors may keep early-career ecologists from realizing the breadth of available positions. We propose an online jobs hub to make non-academic sectors more accessible to ecologists. We also suggest students develop skills portfolios to prepare for non-academic positions. Second, the composition of people who are ecologists differs from broader society, partially due to implicit biases and institutional barriers. We propose steps to reduce attrition of diversity in ecology that include countering implicit biases and creating mentorship networks. We offer steps to improve recruitment by increasing awareness of ecology among high school students and undergraduates and providing opportunities to engage in ecological research. Finally, ecology is only relevant if the public perceives it to be. We must improve science communication and begin cultivating trust. We propose that ad hoc communication by all ecologists is insufficient; translational ecologists should be hired in every department and formal training in translational ecology is necessary. We hope this paper catalyzes critical thinking and partnerships among students, professional ecologists, and the ESA to ensure the future of ecology is vibrant.
Land use change and El Niño-Southern Oscillation drive decadal carbon balance shifts in Southeast Asia
(2018-03) Kondo, Masayuki; Ichii, Kazuhito; Patra, Prabir K.; Canadell, Joseph G.; Poulter, Benjamin; Stitch, Stephen; Calle, Leonardo; Liu, Yi Y.; van Dijk, Albert I. J. M.; Saeki, Tazu; Saigusa, Nobuko; Friedlingstein, Pierre; Arneth, Almut; Harper, Anna B.; Jain, Atul K.; Kato, Etsushi; Koven, Charles D.; Li, Fang; Pugh, Thomas A. M.; Zaehle, Sonke; Wiltshire, Andy; Chevallier, Frederic; Maki, Takashi; Nakamura, Takashi; Niwa, Yosuke; Rödenbeck, Christian
An integrated understanding of the biogeochemical consequences of climate extremes and land use changes is needed to constrain land-surface feedbacks to atmospheric CO2 from associated climate change. Past assessments of the global carbon balance have shown particularly high uncertainty in Southeast Asia. Here, we use a combination of model ensembles to show that intensified land use change made Southeast Asia a strong source of CO2 from the 1980s to 1990s, whereas the region was close to carbon neutral in the 2000s due to an enhanced CO2 fertilization effect and absence of moderate-to-strong El Niño events. Our findings suggest that despite ongoing deforestation, CO2 emissions were substantially decreased during the 2000s, largely owing to milder climate that restores photosynthetic capacity and suppresses peat and deforestation fire emissions. The occurrence of strong El Niño events after 2009 suggests that the region has returned to conditions of increased vulnerability of carbon stocks.
Regional Carbon Fluxes from Land Use and Land Cover Change in Asia, 1980-2009
(2016-07) Calle, Leonardo; Canadell, Josep; Patra, Prabir K.; Ciais, Philippe; Ichii, Kazuhito; Tian, Hui; Kondo, Masayuki; Piao, Shilong; Arneth, Almut; Harper, Anna B.
We present a synthesis of the land-atmosphere carbon flux from land use and land cover change (LULCC) in Asia using multiple data sources and paying particular attention to deforestation and forest regrowth fluxes. The data sources are quasi-independent and include the U.N. Food and Agriculture Organization-Forest Resource Assessment (FAO-FRA 2015; country-level inventory estimates), the Emission Database for Global Atmospheric Research (EDGARv4.3), the 'Houghton' bookkeeping model that incorporates FAO-FRA data, an ensemble of 8 state-of-the-art Dynamic Global Vegetation Models (DGVM), and 2 recently published independent studies using primarily remote sensing techniques. The estimates are aggregated spatially to Southeast, East, and South Asia and temporally for three decades, 1980–1989, 1990–1999 and 2000–2009. Since 1980, net carbon emissions from LULCC in Asia were responsible for 20%–40% of global LULCC emissions, with emissions from Southeast Asia alone accounting for 15%–25% of global LULCC emissions during the same period. In the 2000s and for all Asia, three estimates (FAO-FRA, DGVM, Houghton) were in agreement of a net source of carbon to the atmosphere, with mean estimates ranging between 0.24 to 0.41 Pg C yr−1, whereas EDGARv4.3 suggested a net carbon sink of −0.17 Pg C yr−1. Three of 4 estimates suggest that LULCC carbon emissions declined by at least 34% in the preceding decade (1990–2000). Spread in the estimates is due to the inclusion of different flux components and their treatments, showing the importance to include emissions from carbon rich peatlands and land management, such as shifting cultivation and wood harvesting, which appear to be consistently underreported.
The role of land use change and land management in the global carbon cycle: simulation as a test of process understanding
(Montana State University - Bozeman, College of Letters & Science, 2019) Calle, Leonardo; Chairperson, Graduate Committee: David Roberts and Benjamin Poulter (co-chair); Josep G. Canadell, Prabir Patra, Philippe Ciais, Kazuhito Ichii, Hanqin Tian, Masayuki Kondo, Shilong Piao, Almut Arneth, Anna B. Harper, Akihiko Ito, Etsushi Kato, Charlie Koven, Stephen Sitch, Benjamin D. Stocker, Nicolas Vivoy, Andy Wiltshire, Sonke Zaehle and Benjamin Poulter were co-authors of the article, 'Regional carbon fluxes from land use and land cover change in Asia, 1980-2009' in the journal 'Environmental research letters' which is contained within this dissertation.; Prabir Patra and Benjamin Poulter were co-authors of the article, 'A segmentation algorithm for characterizing rise and fall segments in seasonal cycles: an application to XCO 2 to estimate benchmarks and assess model bias' in the journal 'Atmospheric measurement techniques discussions' which is contained within this dissertation.
Humans have left their mark on Earth's ecosystems for centuries. Since 1900, the human population has grown more than 400%. Land conversion and land management have helped meet an ever-increasing demand for natural resources. Forests have been cleared for agriculture, grasslands have been used for grazing by farmed animals, and extensive logging activity has provided fuelwood for energy and raw materials for building. But a long history of land management has also led to a change in forest production, leaving century-old legacies of human activity on Earth's ecosystems. As land is deforested, wood can be used for building or other products. Unused biomass can be burned for fuel or naturally broken down by microbes into soils, ultimately being converted to carbon dioxide. This phase conversion of carbon, from solid to gas, is a natural process but humans have sped up this process, leading to more carbon dioxide in the atmosphere than would otherwise occur naturally. Increasing levels of carbon dioxide in the atmosphere is a direct cause of increasing global temperatures and changes to regional climates. For these reasons, the focus of research in this Dissertation has been to track each and every process during land use change and land management, to provide a better accounting of where and how much carbon gets transferred from solid to gas during land use activities, and to identify any alteration to the productivity of ecosystems long after timber harvest has removed wood for products or agricultural lands have been abandoned and the forest allowed to regrow. The research papers in Chapter Two and Three have been published in peer-reviewed scientific journals, and Chapter Four is prepared for submission for publication. Each chapter focuses on a very specific problem, but the thread connecting all these works is carbon -- How much carbon is transferred to a gas when natural lands are modified and resources extracted to meet human demand? Does deforestation leave a unique and long-lasting signal in the atmosphere? Land management creates more young, fast-growing forests, but can models represent forests of different ages at global scales?
Toward spatio-temporal delineation of positive interactions in ecology
(2020-09) Tumolo, Benjamin B.; Calle, Leonardo; Anderson, Heidi E.; Briggs, Michelle A.; Carlson, Samuel P.; MacDonald, Michael J.; Reinert, James Holden; Albertson, Lindsey K.
Given unprecedented rates of biodiversity loss, there is an urgency to better understand the ecological consequences of interactions among organisms that may lost or altered. Positive interactions among organisms of the same or different species that directly or indirectly improve performance of at least one participant can structure populations and communities and control ecosystem process. However, we are still in need of synthetic approaches to better understand how positive interactions scale spatio-temporally across a range of taxa and ecosystems. Here, we synthesize two complementary approaches to more rigorously describe positive interactions and their consequences among organisms, across taxa, and over spatio-temporal scales. In the first approach, which we call the mechanistic approach, we make a distinction between two principal mechanisms of facilitation—habitat modification and resource modification. Considering the differences in these two mechanisms is critical because it delineates the potential spatio-temporal bounds over which a positive interaction can occur. We offer guidance on improved sampling regimes for quantification of these mechanistic interactions and their consequences. Second, we present a trait-based approach in which traits of facilitators or traits of beneficiaries can modulate their magnitude of effect or how they respond to either of the positive interaction mechanisms, respectively. Therefore, both approaches can be integrated together by quantifying the degree to which a focal facilitator's or beneficiary's traits explain the magnitude of a positive effect in space and time. Furthermore, we demonstrate how field measurements and analytical techniques can be used to collect and analyze data to test the predictions presented herein. We conclude by discussing how these approaches can be applied to contemporary challenges in ecology, such as conservation and restoration and suggest avenues for future research.