Alejandro de la Fuente

Alejandro de la Fuente

PhD candidate

Talks and presentations

Possums in Peril: The Urgent Need to Address Climate Change Impacts on Tropical Montane Species

November 04, 2023

Talk, TESS conference, Palm Cove, Australia

Abstract - Even in our most protected havens, the relentless pace of climate change poses a grave threat. In mountain ecosystems such as the Australian Wet Tropics, the struggle against climate change is an uphill battle. Rising temperatures force ringtail possums higher up the mountains in search of cooler climates. However, the climbing race becomes particularly challenging for species already living near the mountaintops, such as the ringtail possums of the Wet Tropics, leaving them with nowhere to escape the impacts of climate change. Today, ringtail possums persist in critical numbers at high elevations, standing on the brink of survival.

Songs of disappearance: Rainforest Montane Birds and Climate Change

October 15, 2023

Talk, Zoology and Ecology North Queensland, Mission Beach, Australia

Abstract - Climate-driven biodiversity erosion is escalating at an alarming rate. The pressure imposed by climate change is exceptionally high in tropical ecosystems, where species adapted to narrow environmental ranges exhibit strong physiological constraints. Despite the observed detrimental effect of climate change on ecosystems at a global scale, our understanding of the extent to which multiple climatic drivers affect population dynamics is limited. Here, we disentangle the impact of different climatic stressors on 47 rainforest birds inhabiting the mountains of the Australian Wet Tropics using hierarchical population models. We estimate the effect of spatiotemporal changes in temperature, precipitation, heatwaves, droughts and cyclones on the population dynamics of rainforest birds between 2000 and 2016. We find a strong effect of warming and changes in rainfall patterns across the elevational-segregated bird communities, with lowland populations benefiting from increasing temperature and precipitation, while upland species show an inverse strong negative response to the same drivers. Additionally, we find a negative effect of heatwaves on lowland populations, a pattern associated with the observed distribution of these extreme events across elevations. In contrast, cyclones and droughts have a marginal effect on spatiotemporal changes in rainforest bird communities, suggesting a species-specific response unrelated to the elevational gradient. This study demonstrated the importance of unravelling the drivers of climate change impacts on population changes, providing significant insight into the mechanisms accelerating climate-induced biodiversity degradation.

Crisis in the tropics: Signs of an imminent collapse

August 08, 2023

Talk, CBCS - University of Queensland, Brisbane, Australia

Abstract - Long-term research on the impact of climate change on tropical montane biodiversity in the Australian Wet Tropics holds profound implications for our understanding of the escalating crisis. Results from more than thirty years of monitoring effort in the rainforest of north-east Queensland demonstrate that climate change is driving biodiversity erosion at an alarming rate, particularly affecting species with narrow environmental ranges. Rising temperatures and increasing frequency of extreme heatwaves pose severe threats to the population dynamics of various species, leading to rapid declines and even local extinctions. Furthermore, the observed changes in distribution and abundance of species underscore the urgency to address the vulnerability of montane ecosystems worldwide. This research highlights the critical importance of unravelling the drivers of climate change impacts on population changes, offering significant insight into the mechanisms accelerating climate-induced biodiversity degradation. The findings serve as a wake-up call for immediate action to preserve these fragile ecosystems and the irreplaceable biodiversity they support. As we face the consequences of a changing climate, this research provides a compelling foundation for the development of effective conservation strategies and policies to safeguard tropical montane biodiversity for generations to come.

The impact of climate change in the Australian Wet Tropics

December 05, 2022

Talk, Climate and Metabolic Ecology Lab, University of Melbourne, Melbourne, Australia

Abstract - The increasing frequency and intensity of extreme weather escalate the pressure of global warming on biodiversity. Globally, synergistic effects of multiple components of climate change have driven local extinctions and community collapses, raising concern about the irreversible deterioration of ecosystems. Here, we disentangle the pressure of increasing warming and frequency of extreme heatwaves on the population dynamics of tropical ringtail possums (family: Pseudocheiridae). Ringtail possums’ population dynamics were estimated between 1992 and 2021 using a hierarchical population model that explicitly described the state process and accounted for imperfect detection. Under our model, we propagated the estimated mechanisms governing the system by forecasting ringtails’ population dynamics between 2022 and 2050. Derived from this process, we calculated the probability of absolute and quasi-extinction using different population viability thresholds. We find a strong negative effect of climate change on population dynamics, particularly extreme heatwaves, resulting in a rapid and severe decline in ringtails’ population size in the last three decades. Forecasted increases in temperature and heatwaves threaten the collapse of rain forest ringtail possums by 2050, with populations falling below viability thresholds within three decades.

Predicted alteration of vertebrate communities in response to climate-induced elevational shifts

November 25, 2022

Talk, ESA-SCBO conference, Wollongong, Australia

Abstract - Climate change is driving species to migrate to novel areas as current environments become unsuitable. As a result, species distributions have shifted uphill in montane ecosystems globally. Heterogeneous dispersal rates among shifting species could result in complex changes to community assemblages. For example, interspecific differences in dispersal ability could lead to the disruption, or creation, of species interactions and processes within communities, likely amplifying the impact of climate change on ecosystems. Here, we studied the dispersal success of vertebrate species in a tropical montane ecosystem under a climate-induced uphill shift and assessed the derived impacts on community structures. We simulated the uphill shift of 7613 community assemblages across the elevational gradient using thermal resistance layers for movement analyses. Dispersal success was calculated as the probability of shifting given species’ dispersal ability and landscape composition. We then used dissimilarity indices to measure the potential changes in community structures resulting from the heterogeneous dispersal success among migrating species. Dispersal success was strongly influenced by species’ dispersal ability, landscape composition and climate change. The heterogeneous dispersal success among migrating species induced marked temporal changes between community assemblages along the elevational gradient. The local extinction rate (i.e. the proportion of species unable to shift) was especially remarkable at high elevations, suggesting potential mass local extinctions of upland species. Furthermore, the increasing local extinction rate with elevation resulted in substantial declines in species co-occurrence in high-altitude ecosystems. Our study highlights the escalating impact of climate change on community assemblages in response to climate-induced elevational shifts, providing a classic example of the “escalator to extinction.” Future predictions of the impacts of climate change on ecosystems will benefit from improvements in understanding species interactions, population dynamics and species potential to adapt to a changing environment.

Climate change threatens the future of rainforest ringtail possums

October 16, 2022

Talk, Zoology and Ecology North Queensland Conference, Mission Beach, Australia

Abstract - The increasing frequency and intensity of extreme weather escalate the pressure of global warming on biodiversity. Globally, synergistic effects of multiple components of climate change have driven local extinctions and community collapses, raising concern about the irreversible deterioration of ecosystems. Here, we disentangle the pressure of increasing warming and frequency of extreme heatwaves on the population dynamics of tropical ringtail possums (family: Pseudocheiridae). Ringtail possums’ population dynamics were estimated between 1992 and 2021 using a hierarchical population model that explicitly described the state process and accounted for imperfect detection. Under our model, we propagated the estimated mechanisms governing the system by forecasting ringtails’ population dynamics between 2022 and 2050. Derived from this process, we calculated the probability of absolute and quasi-extinction using different population viability thresholds. We find a strong negative effect of climate change on population dynamics, particularly extreme heatwaves, resulting in a rapid and severe decline in ringtails’ population size in the last three decades. Forecasted increases in temperature and heatwaves threaten the collapse of rain forest ringtail possums by 2050, with populations falling below viability thresholds within three decades.

Introduction to hierarchical models for abundance

August 22, 2022

Talk, CodeR, James Cook University, Townsville, Australia

Introduction to hierarchical models for abundance - This talk aims to introduce one of the most powerful models to estimate population size from survey data, an essential skill in any ecologist’s toolkit. I will show how it is possible to estimate abundance while accounting for imperfect detection, and we will discuss the implications of this. This model is particularly useful to infer population size from counts of unmarked individuals, although its flexibility allows complex modifications to fit a huge variety of ecological data.

Predicting species abundance by implementing the ecological niche theory

November 03, 2021

Talk, Annual conference of the Centre for Tropical Environmental and Sustainability Science, James Cook University, Cairns, Australia

Abstract - Species are not uniformly distributed across the landscape. For every species, there should be few favoured sites where abundance is high and many other sites of lower suitability where abundance is low. Consequently, local abundance could be thought of as a natural expression of species response to local conditions. The correlation between abundance and environmental suitability has been well documented, and a recent meta-analysis has suggested that this relationship could be a generality. Despite the importance and potential implication of the abundance–suitability relationship, its predictive power for meaningful extrapolations has been surprisingly poorly explored. In this study, we showed how a highly predictable trend can be extracted from the abundance–suitability relationship, accurately predicting the variation in species abundance at a high spatial resolution. We produced high-quality environmental suitability estimations for 50 endemic species in the Australian Wet Tropics. Environmental suitability derived from species distribution models was related to observed abundance estimated using data from 29 years of uninterrupted monitoring effort. We used the fitted relationship to accurately predict abundance at a fine scale across the species range. Our results showed that the abundance–suitability relationship was strong for endemic species in the Australian Wet Tropics. The predictive power of our models was high, explaining, on average, 55% of the deviance across taxa. Despite interspecific variation in the strength of the abundance–suitability relationship associated with potential intrinsic estimation biases, our approach provides a powerful tool for predicting abundance across the species range at a fine scale. The potential for robust abundance predictions from occurrence-based species distribution models shown in this study are numerous, and it could have a significant impact in enhancing species conservation and management decisions.

Seasonal variation in the richness, relative frequency and diversity of birds in urban wetlands of Llanquihue, southern Chile

November 21, 2017

Poster, XXII Congress of Chilean Ornithology, Santa Cruz, Chile

Abstract - Between 2017 and 2018 we evaluated the seasonal variation in richness, recorded frequency, proportional diversity, and community similarity of birds in three wetlands located within of Llanquihue city. We estimate the richness and recorded the frequency of birds observed in nine count points (observation time = 10 min, visual angle = 170º, detection radius = 40 m) located at the edge of each wetland (three points per wetland). All counts were made during the morning (08:30-12:00). We determined the local and seasonal avian diversity based on two indices: species evenness (J’) and species dominance (λ). We used the Jaccard coefficient (Cj) to determine the community similarity. We registered 50 species of which 55% are residents and 20% breed in Llanquihue. The Laguna El Loto showed the lowest richness (30 species), and the Laguna Las Ranas the higher richness (35 species). The diversity tended to be high in all studied wetlands (0.50 < Jʼ < 0.78; 0.09 < λ’ < 0.30), and their bird assemblages were very similar to each other (Cj > 0.77 in all pairs compared). We registered the highest species richness in spring and the lowest in autumn (35 and 24 species, respectively). During all the seasons, the most frequently observed species were the Neotropic Cormorants, Black-crowned Night-heron, Southern Lapwing, Speckled Teal, and Brown-hooded Gull. Species diversity was high throughout the year (0.10 < λ’< 0.25, 0.56 < J’ < 0.78). Our study shows that the wetland network of Llanquihue city contains a high avifaunal diversity, and despite the effect of urbanization, it remains an ecologically productive ecosystem.