Network


Latest external collaboration on country level. Dive into details by clicking on the dots.

Hotspot


Dive into the research topics where Rodrigo Sierra is active.

Publication


Featured researches published by Rodrigo Sierra.


World Development | 1991

The causes of tropical deforestation in Ecuador: A statistical analysis

Douglas Southgate; Rodrigo Sierra; Lawrence A. Brown

Abstract This paper reports a statistical analysis of the causes of agricultural colonization and land clearing in eastern Ecuador. The results bolster many of the arguments that have been made about the social forces driving tropical deforestation. In general, the prospect of capturing agricultural rents stimulates settlement of tree-covered hinterlands. Accordingly, the presence of roads and urban centers attracts rural settlement. Colonists also prefer to go where soils are suitable for crop or livestock production, all else remaining the same. In addition to being a function of population pressure, the extent of land clearing is shown to be a consequence of tenure insecurity. These results suggest that institutional reform is needed to encourage conservation of tropical forests.


Landscape and Urban Planning | 2002

Assessing biodiversity conservation priorities: ecosystem risk and representativeness in continental Ecuador

Rodrigo Sierra; Felipe Campos; Jordan Chamberlin

Abstract Setting conservation priorities with a geographic vision is essential in developing countries due to limited resources for conservation and the urgency of establishing new reserves. Priorities should reflect the risk ecosystems are facing and how represented they are in current national reserve networks (NRN). Conservation planning, research, and reserve design should focus on priority ecosystems. This study identified the priority ecosystems for the conservation of continental Ecuador’s biodiversity using a multi-criteria model developed in collaboration with Ecuador’s Ministry of the Environment. This model ranked ecosystems based on four conditions: representativeness in the current reserve network, human pressure, habitat loss, and species-level value based on bird species data. Results show that although Ecuador’s reserve network covers approximately 14% of the country, several ecosystems are poorly represented using a conservative 10% level benchmark, while others are not included at all. In general, highly diverse, humid environments are well represented while low-diversity, dry environments, are poorly represented. These low-diversity, low-representation ecosystems are also the most threatened. Conservation programs and new reserves design in continental Ecuador should concentrate on these ecosystems until the desired representativeness is attained. These results were formally presented to Ecuador’s Ministry of the Environment in 2000. This study shows that an ecosystem-risk-representativeness approach can be implemented efficiently at scales that take advantage of limited resources yet are effective for policy and planning. Current technologies can be used effectively to map major ecosystems, and to assess various forms of risk and representativeness in reasonable time for a country or a large region.


Environment and Planning A | 1992

Complementary Perspectives as a Means of Understanding Regional Change: Frontier Settlement in the Ecuador Amazon

Lawrence A. Brown; Rodrigo Sierra; Douglas Southgate; L Labao

Illustrated in this paper is a research protocol wherein regional change in the Ecuador Amazon, measured in terms of changing settlement patterns, is explored from three distinct but complementary vantage points—idiographic, context-dependent generalizations, and universally applicable frameworks. All analyses are anchored to the study area itself; the regions ground-level reality plays a prominent role throughout; and the Amazon as a place is the object of study. The more universal the explanation, the less information it provides about the Ecuador Amazon per se; but each conceptualization illuminates a distinct aspect of the Amazon experience. A comprehensive understanding is the end result. The research protocol is situated within current concerns over place, the new regional geography, and related research strategies.


Biodiversity and Conservation | 2007

Identification of Biodiversity Conservation Priorities using Predictive Modeling: An Application for the Equatorial Pacific Region of South America

Manuel Peralvo; Rodrigo Sierra; Kenneth R. Young; Carmen Ulloa Ulloa

We used predictive modeling of species distributions to identify conservation priority areas in the equatorial Pacific region of western Ecuador and northwestern Peru. Museum and herbarium data and predictive models of species distributions are increasingly being used to assess the conservation status of individual species. In this study, we assembled occurrence data for 28 species of vascular plants, birds, and mammals to assess the conservation priorities of the set of natural communities that they represent. Environmental variables were used to predict the species’ distributions using correlative modeling as an alternative to point data, which has been the traditional approach to identify critical areas. Specific priority sites for conservation were identified using an area-selection algorithm based on simulated annealing. Four scenarios of prioritization were created using different criteria for the spatial compactness of the selected sites and fragmentation of remnant habitat. The results provide a preliminary assessment of conservation priorities for the dry ecosystems of the Equatorial Pacific region, and will serve as guidelines to focus future fieldwork.


Ecography | 2017

Seasonal drought limits tree species across the Neotropics

Adriane Esquivel-Muelbert; Timothy R. Baker; Kyle G. Dexter; Simon L. Lewis; Hans ter Steege; Gabriela Lopez-Gonzalez; Abel Monteagudo Mendoza; Roel J. W. Brienen; Ted R. Feldpausch; Nigel C. A. Pitman; Alfonso Alonso; Geertje M.F. van der Heijden; Marielos Peña-Claros; Manuel Ahuite; Miguel Alexiaides; Esteban Álvarez Dávila; Alejandro Araujo Murakami; Luzmila Arroyo; Milton Aulestia; Henrik Balslev; Jorcely Barroso; Rene G. A. Boot; Ángela Cano; Victor Chama Moscoso; James A. Comiskey; Fernando Cornejo; Francisco Dallmeier; Douglas C. Daly; Nállarett Dávila; Joost F. Duivenvoorden

Within the tropics, the species richness of tree communities is strongly and positively associated with precipitation. Previous research has suggested that this macroecological pattern is driven by the negative effect of water-stress on the physiological processes of most tree species. This process implies that the range limits of taxa are defined by their ability to occur under dry conditions, and thus in terms of species distributions it predicts a nested pattern of taxa distribution from wet to dry areas. However, this ‘dry-tolerance’ hypothesis has yet to be adequately tested at large spatial and taxonomic scales. Here, using a dataset of 531 inventory plots of closed canopy forest distributed across the Western Neotropics we investigated how precipitation, evaluated both as mean annual precipitation and as the maximum climatological water deficit, influences the distribution of tropical tree species, genera and families. We find that the distributions of tree taxa are indeed nested along precipitation gradients in the western Neotropics. Taxa tolerant to seasonal drought are disproportionally widespread across the precipitation gradient, with most reaching even the wettest climates sampled; however, most taxa analysed are restricted to wet areas. Our results suggest that the ‘dry tolerance’ hypothesis has broad applicability in the worlds most species-rich forests. In addition, the large number of species restricted to wetter conditions strongly indicates that an increased frequency of drought could severely threaten biodiversity in this region. Overall, this study establishes a baseline for exploring how tropical forest tree composition may change in response to current and future environmental changes in this region.


Scientific Reports | 2015

Memory reconsolidation may be disrupted by a distractor stimulus presented during reactivation.

Ana Paula Crestani; Flávia Zacouteguy Boos; Josué Haubrich; Rodrigo Sierra; Fabiana Santana; Johanna Marcela Duran Molina; Lindsey de Freitas Cassini; Lucas de Oliveira Alvares; Jorge Alberto Quillfeldt

Memories can be destabilized by the reexposure to the training context, and may reconsolidate into a modified engram. Reconsolidation relies on some particular molecular mechanisms involving LVGCCs and GluN2B-containing NMDARs. In this study we investigate the interference caused by the presence of a distractor - a brief, unanticipated stimulus that impair a fear memory expression - during the reactivation session, and tested the hypothesis that this disruptive effect relies on a reconsolidation process. Rats previously trained in the contextual fear conditioning (CFC) were reactivated in the presence or absence of a distractor stimulus. In the test, groups reactivated in the original context with distractor displayed a reduction of the freezing response lasting up to 20 days. To check for the involvement of destabilization / reconsolidation mechanisms, we studied the effect of systemic nimodipine (a L-VGCC blocker) or intra-CA1 ifenprodil (a selective GluN2B/NMDAR antagonist) infused right before the reactivation session. Both treatments were able to prevent the disruptive effect of distraction. Ifenprodil results also bolstered the case for hippocampus as the putative brain structure hosting this phenomenon. Our results provide some evidence in support of a behavioral, non-invasive procedure that was able to disrupt an aversive memory in a long-lasting way.


Ecology and Evolution | 2014

Are all species necessary to reveal ecologically important patterns

Edwin Theodoor Pos; Juan Ernesto Guevara Andino; Daniel Sabatier; Jean François Molino; Nigel C. A. Pitman; Hugo Mogollón; David A. Neill; Carlos Cerón; Gonzalo Rivas; Anthony Di Fiore; Raquel Thomas; Milton Tirado; Kenneth R. Young; Ophelia Wang; Rodrigo Sierra; Roosevelt García-Villacorta; Roderick Zagt; Walter A. Palacios; Milton Aulestia; Hans ter Steege

While studying ecological patterns at large scales, ecologists are often unable to identify all collections, forcing them to either omit these unidentified records entirely, without knowing the effect of this, or pursue very costly and time-consuming efforts for identifying them. These “indets” may be of critical importance, but as yet, their impact on the reliability of ecological analyses is poorly known. We investigated the consequence of omitting the unidentified records and provide an explanation for the results. We used three large-scale independent datasets, (Guyana/ Suriname, French Guiana, Ecuador) each consisting of records having been identified to a valid species name (identified morpho-species – IMS) and a number of unidentified records (unidentified morpho-species – UMS). A subset was created for each dataset containing only the IMS, which was compared with the complete dataset containing all morpho-species (AMS: = IMS + UMS) for the following analyses: species diversity (Fishers alpha), similarity of species composition, Mantel test and ordination (NMDS). In addition, we also simulated an even larger number of unidentified records for all three datasets and analyzed the agreement between similarities again with these simulated datasets. For all analyses, results were extremely similar when using the complete datasets or the truncated subsets. IMS predicted ≥91% of the variation in AMS in all tests/analyses. Even when simulating a larger fraction of UMS, IMS predicted the results for AMS rather well. Using only IMS also out-performed using higher taxon data (genus-level identification) for similarity analyses. Finding a high congruence for all analyses when using IMS rather than AMS suggests that patterns of similarity and composition are very robust. In other words, having a large number of unidentified species in a dataset may not affect our conclusions as much as is often thought.


The Professional Geographer | 2003

Forest-Cover Change from Labor- and Capital-Intensive Commercial Logging in the Southern Chocó Rainforests†

Rodrigo Sierra; Milton Tirado; Walter A. Palacios

Abstract This article examines two key aspects of land-cover change in the south of the Chocó region. First, it assesses and compares the local impact on forest condition of labor-intensive and capital-intensive commercial logging. Second, it assesses the regional significance and permanency of these changes. Studies of land-cover change associated with commercial logging have focused almost exclusively on capital-intensive extraction and have assumed that after logging, degraded forests are transformed into agricultural cover. This study shows that both capital- and labor-intensive logging result in similar land-cover changes (i.e., forest degradation) if the timber sought is the same. However, labor-intensive loggers also seek timber species not sought by capital-intensive loggers, and this impact is statistically different from the impact of the extraction of the first group of species. Results also show that only a small fraction (20–30 percent) of the area logged is later converted to agricultural cover types. The persistence of logged forests means that up to 20 percent of the remaining forest cover could correspond to forests with significant and lasting levels of degradation. Furthermore, the different production requirements for each group of species also mean that there is a spatial differentiation in the impact of logging in the region. Logged forests are arranged into two consecutive corridors on each side of access routes (e.g., rivers). The first corridor corresponds to a narrow (approximately 1-km) band of high-intensity degradation. The second, broader (approximately 2-km) forest band, with lower levels of degradation, extends inland along first-tier corridors. A key factor determining the permanency of this land-cover pattern is the strong control local communities have over the land in the region. This limits the spread of patterns observed in other frontier areas, especially the conversion of logged forests into agricultural cover.


Geographical Review | 2013

LANDSCAPE CHANGE IN WESTERN AMAZONIA

Santiago López; Rebecca Beard; Rodrigo Sierra

Changes in settlement patterns have influenced food‐production systems and territorial organization in western Amazonia, and landing strips have affected current land‐use patterns in indigenous territories in the region. In this study we characterize riverine and interfluvial production systems in the lower Pastaza River Basin in Ecuador, using historical ethnographic records, remotely sensed data, surveyed information, and statistical descriptions. Results show that nucleation of settlements around landing strips has increased indigenous peoples control over their ancestral territories and changed the political and geographical landscape. At the same time, nucleation is slowly transforming indigenous livelihoods from mobile cultivation and foraging to sedentary farming. Even though indigenous communities will eventually become integrated into the national economy, the main elements of the traditional food‐production system will likely remain the same. Development policies should respond to local land‐management strategies in order to ensure the long‐term sustainability of Amazonian socioecological systems.


Ecology and Evolution | 2017

Estimating and interpreting migration of Amazonian forests using spatially implicit and semi-explicit neutral models

Edwin Theodoor Pos; Juan Ernesto Guevara Andino; Daniel Sabatier; Jean-François Molino; Nigel C. A. Pitman; Hugo Mogollón; David A. Neill; Carlos Cerón; Gonzalo Rivas-Torres; Anthony Di Fiore; Raquel Thomas; Milton Tirado; Kenneth R. Young; Ophelia Wang; Rodrigo Sierra; Roosevelt García-Villacorta; Roderick Zagt; Walter Palacios Cuenca; Milton Aulestia; Hans ter Steege

Abstract With many sophisticated methods available for estimating migration, ecologists face the difficult decision of choosing for their specific line of work. Here we test and compare several methods, performing sanity and robustness tests, applying to large‐scale data and discussing the results and interpretation. Five methods were selected to compare for their ability to estimate migration from spatially implicit and semi‐explicit simulations based on three large‐scale field datasets from South America (Guyana, Suriname, French Guiana and Ecuador). Space was incorporated semi‐explicitly by a discrete probability mass function for local recruitment, migration from adjacent plots or from a metacommunity. Most methods were able to accurately estimate migration from spatially implicit simulations. For spatially semi‐explicit simulations, estimation was shown to be the additive effect of migration from adjacent plots and the metacommunity. It was only accurate when migration from the metacommunity outweighed that of adjacent plots, discrimination, however, proved to be impossible. We show that migration should be considered more an approximation of the resemblance between communities and the summed regional species pool. Application of migration estimates to simulate field datasets did show reasonably good fits and indicated consistent differences between sets in comparison with earlier studies. We conclude that estimates of migration using these methods are more an approximation of the homogenization among local communities over time rather than a direct measurement of migration and hence have a direct relationship with beta diversity. As betadiversity is the result of many (non)‐neutral processes, we have to admit that migration as estimated in a spatial explicit world encompasses not only direct migration but is an ecological aggregate of these processes. The parameter m of neutral models then appears more as an emerging property revealed by neutral theory instead of being an effective mechanistic parameter and spatially implicit models should be rejected as an approximation of forest dynamics.

Collaboration


Dive into the Rodrigo Sierra's collaboration.

Top Co-Authors

Avatar
Top Co-Authors

Avatar

Milton Tirado

University of Texas at Austin

View shared research outputs
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar

Kenneth R. Young

University of Texas at Austin

View shared research outputs
Top Co-Authors

Avatar

Daniel Sabatier

Institut de recherche pour le développement

View shared research outputs
Top Co-Authors

Avatar
Top Co-Authors

Avatar

Anthony Di Fiore

University of Texas at Austin

View shared research outputs
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Researchain Logo
Decentralizing Knowledge