Habitat destruction and overexploitation are the main threats to biodiversity and where they co‐occur, their combined impact is often larger than their individual one. Yet, detailed knowledge of the ...spatial footprints of these threats is lacking, including where they overlap and how they change over time. These knowledge gaps are real barriers for effective conservation planning. Here, we develop a novel approach to reconstruct the individual and combined footprints of both threats over time. We combine satellite‐based land‐cover change maps, habitat suitability models and hunting pressure models to demonstrate our approach for the community of larger mammals (48 species > 1 kg) across the 1.1 million km2 Gran Chaco region, a global deforestation hotspot covering parts of Argentina, Bolivia and Paraguay. This provides three key insights. First, we find that the footprints of habitat destruction and hunting pressure expanded considerably between 1985 and 2015, across ~40% of the entire Chaco – twice the area affected by deforestation. Second, both threats increasingly acted together within the ranges of larger mammals in the Chaco (17% increase on average, ± 20% SD, cumulative increase of co‐occurring threats across 465 000 km2), suggesting large synergistic effects. Conversely, core areas of high‐quality habitats declined on average by 38%. Third, we identified remaining priority areas for conservation in the northern and central Chaco, many of which are outside the protected area network. We also identify hotspots of high threat impacts in central Paraguay and northern Argentina, providing a spatial template for threat‐specific conservation action. Overall, our findings suggest increasing synergistic effects between habitat destruction and hunting pressure in the Chaco, a situation likely common in many tropical deforestation frontiers. Our work highlights how threats can be traced in space and time to understand their individual and combined impact, even in situations where data are sparse.
Land-use change is a global threat to biodiversity, but how land-use change affects species beyond the direct effect of habitat loss remains poorly understood. We developed an approach to isolate and ...map the direct and indirect effects of agricultural expansion on species of conservation concern, using the threatened giant anteater (
Myrmecophaga tridactyla
) in the Gran Chaco as an example. We reconstructed anteater occupancy change between 1985 and 2015 by fitting single-season occupancy models with contemporary camera-trap data and backcasting the models to 1985 and 2000 land-cover/use maps. Based on this, we compared the area of forest loss (direct effect of agricultural expansion) with the area where forests remained but occupancy still declined (indirect effect of agricultural expansion). Anteater occupancy decreased substantially since 1985, particularly after 2000 when agriculture expanded rapidly. Between 1985 and 2015, ~ 64,000 km
2
of forest disappeared, yet occupancy declined across a larger area (~ 102,000 km
2
), extending far into seemingly untransformed habitat. This suggests that widespread sink habitat has emerged due to agricultural land-use change, and that species may lose their habitat through direct and indirect effects of agricultural expansion, highlighting the urgent need for broad-scale conservation planning in the Chaco. Appropriate management responses could proactively protect more habitat where populations are stable, and restore habitat or address causes of mortality in areas where declines occur. Our work also highlights how occupancy modelling combined with remote sensing can help to detect the direct and indirect effects of agricultural expansion, providing guidance for spatially targeting conservation strategies to halt extinctions.
1. Habitat loss is the primary cause of local extinctions. Yet, there is considerable uncertainty regarding how fast species respond to habitat loss, and how time-delayed responses vary in space. 2. ...We focused on the Argentine Dry Chaco (c. 32 million ha), a global deforestation hotspot, and tested for time-delayed response of bird and mammal communities to landscape transformation. We quantified the magnitude of extinction debt by modelling contemporary species richness as a function of either contemporary or past (2000 and 1985) landscape patterns. We then used these models to map communities' extinction debt. 3. We found strong evidence for an extinction debt: landscape structure from 2000 explained contemporary species richness of birds and mammals better than contemporary and 1985 landscapes. This suggests time-delayed responses between 10 and 25 years. Extinction debt was especially strong for forest specialists. 4. Projecting our models across the Chaco highlighted areas where future local extinctions due to unpaid extinction debt are likely. Areas recently converted to agriculture had highest extinction debt, regardless of the post-conversion land use. Few local extinctions were predicted in areas with remaining larger forest patches. 5. Synthesis and applications. The evidence for an unpaid extinction debt in the Argentine Dry Chaco provides a substantial window of opportunity for averting local biodiversity losses. However, this window may close rapidly if conservation activities such as habitat restoration are not implemented swiftly. Our extinction debt maps highlight areas where such conservation activities should be implemented.
► Density of birds responded to long term but not to short term land use changes. ► Tyrannus savanna and Milvago chimango were more related to annual crops. ► Caracara plancus and Sturnella ...supercilliaris were more related to natural habitat. ► Common pest control related birds adapt to a substantial level of land transformation. ► Remnants of natural habitats are necessary to sustain pest controls services.
In Argentina, the rapid expansion and intensification of row crop production that has occurred during the last 20 years has resulted in the loss of habitat and spatial heterogeneity in agroecosystems. One of the principal effects of industrialized row crop production is the loss of avian diversity and associated ecosystem services that benefit crop production. To better understand the response of bird species to the intensification and expansion of row crop agriculture in Argentina, and the potential effects on the provision of ecosystems services, we analyzed the relationship between short- and long-term changes in agricultural land use on the densities of six bird species (Milvago chimango, Caracara plancus, Tyrannus savana, Zenaida auriculata, Molothrus bonariensis, and Sturnella supercilliaris) using data from a large-scale, long-term avian monitoring program in central Argentina. Species densities responded individually to long-term landuse changes; T. savana and M. chimango densities were positively related to an increase in the annual cropping area, whereas C. plancus and S. supercilliaris were positively related to the area of non-plowed fields. M. bonariensis and Z. auriculata (considered crop pests) showed a weak relationship with land use. None of the species exhibited response to short-term changes in land-use. Although generalist species can apparently adapt to a diversity of open habitats, species that provide pest control services were also related to semi-natural habitats and thus likely to suffer from land transformation associated with intensive agricultural management. Our results, as well as those found in similar systems, denote strong inferential evidence that the disappearance of remnants of natural and semi-natural habitats in heavily transformed agricultural landscapes will have a substantial negative effect on the provision of pest control services provided by avian abundance and diversity.
Wild aquatic birds are the major reservoir of influenza A virus. Cloacal swabs and feces samples (n = 6595) were collected from 62 bird species in Argentina from 2006 to 2016 and screened for ...influenza A virus. Full genome sequencing of 15 influenza isolates from 6 waterfowl species revealed subtypes combinations that were previously described in South America (H1N1, H4N2, H4N6 (n = 3), H5N3, H6N2 (n = 4), and H10N7 (n = 2)), and new ones not previously identified in the region (H4N8, H7N7 and H7N9). Notably, the internal gene segments of all 15 Argentine isolates belonged to the South American lineage, showing a divergent evolution of these viruses in the Southern Hemisphere. Time-scaled phylogenies indicated that South American gene segments diverged between ~ 30 and ~ 140 years ago from the most closely related influenza lineages, which include the avian North American (PB1, HA, NA, MP, and NS-B) and Eurasian lineage (PB2), and the equine H3N8 lineage (PA, NP, and NS-A). Phylogenetic analyses of the hemagglutinin and neuraminidase gene segments of the H4, H6, and N8 subtypes revealed recent introductions and reassortment between viruses from the Northern and Southern Hemispheres in the Americas. Remarkably and despite evidence of recent hemagglutinin and neuraminidase subtype introductions, the phylogenetic composition of internal gene constellation of these influenza A viruses has remained unchanged. Considering the extended time and the number of sampled species of the current study, and the paucity of previously available data, our results contribute to a better understanding of the ecology and evolution of influenza virus in South America.
Tropical deforestation is a main driver of the global biodiversity crisis. Impact assessments typically focus on species' presence, which means impacts are detected when local extinctions have ...occurred – and thus when it is too late. Here, we pioneer the combined use of two approaches that can detect deforestation impacts earlier, at the level of populations (using occupancy modelling) and at the level of individuals (using stress hormonal indicators). We tested this approach for the collared peccary (Pecari tajacu) in the Argentine Chaco, a global deforestation hotspot. We used camera-trap data to model peccary occupancy in relation to woodland cover and loss, and measured glucocorticoid metabolites in peccary feces to assess individuals' stress level in deforestation areas. We found that peccary occupancy was highest in remote areas with high woodland cover, but low otherwise. Peccaries were typically absent from areas where deforestation had been widespread recently. Where peccaries were present, physiological stress was correlated with the extent of edge between cropland and forest (a proxy for food availability), and not with deforestation. This, and the observation that peccaries disappear quickly as deforestation progresses, suggests that peccaries do not adapt well to the new conditions in deforestation frontiers. In terms of conservation management, our results underpin the importance of protecting large, contiguous woodland blocks to prevent large mammals from going extinct in deforestation frontiers. More broadly, we show how combining stress hormonal indicators and occupancy modelling can provide deep insights into processes underlying local extinctions in dynamic landscapes.
•We linked occupancy models and stress hormone analyses to assess deforestation impacts.•Peccaries disappeared quickly from deforestation landscapes.•Food limitation, not deforestation, was the main factor causing individual stress.•Peccaries in the Chaco have a low resilience towards deforestation.•Large and contiguous woodland patches are needed to protect large mammals in deforestation frontiers.
Land-use change is a root cause of the extinction crisis, but links between habitat change and biodiversity loss are not fully understood. While there is evidence that habitat loss is an important ...extinction driver, the relevance of habitat fragmentation remains debated. Moreover, while time delays of biodiversity responses to habitat transformation are well-documented, time-delayed effects have been ignored in the habitat loss versus fragmentation debate. Here, using a hierarchical Bayesian multi-species occupancy framework, we systematically tested for time-delayed responses of bird and mammal communities to habitat loss and to habitat fragmentation. We focused on the Argentine Chaco, where deforestation has been widespread recently. We used an extensive field dataset on birds and mammals, along with a time series of annual woodland maps from 1985 to 2016 covering recent and historical habitat transformations. Contemporary habitat amount explained bird and mammal occupancy better than past habitat amount. However, occupancy was affected more by the past rather than recent fragmentation, indicating a time-delayed response to fragmentation. Considering past landscape patterns is therefore crucial for understanding current biodiversity patterns. Not accounting for land-use history ignores the possibility of extinction debt and can thus obscure impacts of fragmentation, potentially explaining contrasting findings of habitat loss versus fragmentation studies.
Understanding how biodiversity responds to intensifying agriculture is critical to mitigating the trade‐offs between them. These trade‐offs are particularly strong in tropical and subtropical ...deforestation frontiers, yet it remains unclear how changing landscape context in such frontiers alters agriculture–biodiversity trade–offs.
We focus on the Argentinean Chaco, a global deforestation hotspot, to explore how landscape context shapes trade‐off curves between agricultural intensity and avian biodiversity. We use a space‐for‐time approach and integrate a large field dataset of bird communities (197 species, 234 survey plots), three agricultural intensity metrics (meat yield, energy yield and profit) and a range of environmental covariates in a hierarchical Bayesian occupancy framework.
Woodland extent in the landscape consistently determines how individual bird species, and the bird community as a whole, respond to agricultural intensity. Many species switch in their fundamental response, from decreasing occupancy with increased agricultural intensity when woodland extent in the landscape is low (loser species), to increasing occupancy with increased agricultural intensity when woodland extent is high (winner species).
This suggests that landscape context strongly mediates who wins and loses along agricultural intensity gradients. Likewise, where landscapes change, such as in deforestation frontiers, the very nature of the agriculture–biodiversity trade–offs can change as landscapes transformation progresses.
Synthesis and applications. Schemes to mitigate agriculture–biodiversity trade–offs, such as land sparing or sharing, must consider landscape context. Strategies that are identified based on a snapshot of data risk failure in dynamic landscapes, particularly where agricultural expansion continues to reduce natural habitats. Rather than a single, fixed strategy, adaptive management of agriculture–biodiversity trade–offs is needed in such situations. Here we provide a toolset for considering changing landscape contexts when exploring such trade‐offs. This can help to better align agriculture and biodiversity in tropical and subtropical deforestation frontiers.
Resumen
Comprender cómo la biodiversidad responde a la intensificación agropecuaria es fundamental para alcanzar un balance entre ambas. Esta necesidad es particularmente crítica en las fronteras de deforestación tropicales y subtropicales. Sin embargo, el efecto de las características del paisaje sobre el balance entre agricultura y biodiversidad aun no ha sido estudiado en profundidad.
Para explorar dicho efecto, nos enfocamos en la comunidad de aves del Chaco argentino, un área clave de deforestación global. Utilizamos un método de sustitución “espacio por tiempo”, la integración de un gran conjunto de datos de aves (197 especies, 234 sitios), tres medidas de intensificación agropecuaria (rendimiento de carne, rendimiento energético, ganancia económica) y covariables ambientales en modelos jerárquicos de ocupación con un enfoque Bayesiano.
La respuesta de las aves a la intensificación agropecuaria, a nivel de especie y de comunidad, está fuertemente mediada por la extensión de bosque en el paisaje. Muchas especies cambian su respuesta de manera radical y pasan de disminuir su ocupación a medida que aumenta la intensificación, en un contexto de baja extensión de bosque, a aumentar su ocupación cuando se intensifica la producción agropecuaria y la extensión de bosque en el paisaje es alta.
Los resultados sugieren que las características del paisaje afectan en gran medida qué especies se benefician y cuáles se perjudican a lo largo del gradiente de intensificación agropecuaria. En este sentido, en un paisaje cambiante, como el que se presenta en las fronteras de deforestación, el balance entre conservación y producción es también dinámico y puede cambiar al tiempo que estas transformaciones se suceden.
Síntesis y aplicación. Las estrategias orientadas a lograr el balance entre producción agropecuaria y biodiversidad, tales como separación (land sparing) o integración (land sharing) de tierras para la conservación, deben tener en cuenta las características del paisaje. Utilizar datos específicos de un punto temporal puede resultar inadecuado en paisajes dinámicos, particularmente donde la actividad agropecuaria tiende a reducir los ambientes naturales. En lugar de una estrategia fija, es conveniente implementar un manejo adaptativo que apunte a lograr el mejor balance entre agricultura y biodiversidad. En este estudio proponemos un conjunto de herramientas para mejorar el análisis de este balance cuando los paisajes son dinámicos y para ayudar a definir la estrategia más eficiente en fronteras de deforestación.
Schemes to mitigate agriculture–biodiversity trade–offs, such as land sparing or sharing, must consider landscape context. Strategies that are identified based on a snapshot of data risk failure in dynamic landscapes, particularly where agricultural expansion continues to reduce natural habitats. Rather than a single, fixed strategy, adaptive management of agriculture–biodiversity trade–offs is needed in such situations. Here we provide a toolset for considering changing landscape contexts when exploring such trade‐offs. This can help to better align agriculture and biodiversity in tropical and subtropical deforestation frontiers.
Strong trade-offs between agriculture and the environment occur in deforestation frontiers, particularly in the world's rapidly disappearing tropical and subtropical dry forests. Pathways to mitigate ...these trade-offs are often unclear, as well as how deforestation or different policies alter the option space of available pathways. Using a spatial optimization framework based on linear programming, we develop a landscape-scale possibility frontier describing trade-offs between agricultural profit, biodiversity, and carbon stock for the Argentinean Dry Chaco, a global deforestation hotspot. We use this framework to assess how current land-use zoning, as well as past and future land-use-trajectories, alter the option space to minimize trade-offs between biodiversity, carbon, and agriculture. Our analyses yield four major insights. First, we found substantial co-benefits between biodiversity and carbon, yet strong trade-offs of both with agriculture. Second, development according to the current zoning could lead to highly suboptimal socio-ecological outcomes; our analysis pinpoints how this zoning could be improved. Third, high landscape-scale multifunctionality can be achieved using different land-use strategies, but maintaining >40% of forest is essential in all of them, and silvopasture systems appear to be central for achieving high overall multifunctionality. Finally, our results suggest the window of opportunity is closing rapidly: recent land-use changes since 2000 have rapidly moved the Chaco within the option space, with forest extent declining towards critical thresholds for maintaining balanced, multifunctional landscapes. Our results emphasize that the time for sustainability planning in the Chaco is now. More broadly, we show how multi-criteria optimization can describe dynamic trade-offs between agriculture and the environment at landscape and regional scales. This can help to identify land-system tipping points that, once crossed, would inhibit more sustainable futures, and policies to avoid such potential traps.
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