•We considered attributes of forests at fragment and landscape scales simultaneously.•The structure of the older age classes was not severely affected by fragmentation.•Different groups of species ...respond differently to the fragmentation process.•The recruitment of the species of the middle stratum is affected by fragment size.•The recruitment of the species of the upper stratum is affected by forest cover.
Subtropical Argentinean Chaco forests have been severely deforested and fragmented due to agriculture during the last six decades. The most affected forests are located in areas that are most favorable for crops. This is the case of the semi-deciduous “bosque de tres quebrachos” (“three quebrachos forest”) in southwest of Chaco Province (Argentina), where this study was carried out. The aim of this work was to analyze the fragmentation process, considering spatial (fragments and landscape levels) and temporal (land use changes) scales, studying the effects on the forest structure (density and basal area) and tree recruitment. All trees (adults and saplings) were recorded and measured in 112 plots (400 m2) distributed in 28 forest fragments (0.9–160ha) located at four different landscape samples (4500ha) in one environmentally homogeneous zone (72,804ha). The four landscape samples have different current forest cover (low/high) and different land use history (low/high). Using linear mixed models, we evaluated the effects of current and historic fragment size, landscape forest cover and land use changes on the density and basal area at stand level, and considering the two different strata (upper and middle). Results showed that fragmentation did not severely affect the structure of the older age classes of trees in the remaining fragments but affect the tree recruitment, which could influence over the ability of the forest to perpetuate itself. We found positive relationships between sapling density and fragment size for the tree species of middle stratum, and between sapling density and forest cover at landscape level for the species of upper stratum. Regarding adults, we found a negative relationship between density and historic fragment size, probably related to the past timber harvesting. We concluded that even small fragments of three quebrachos forest and those located in highly deforested landscapes have high conservation value since their structure does not differ from that of the larger fragments or landscapes with higher forest cover. Our results reveal the importance of considering landscape and fragment scales simultaneously to better understand the fragmentation process and improve the recommendations for the management of fragmented landscapes.
Agricultural expansion threatens biodiversity due to habitat loss and fragmentation. In the Gran Chaco, a global deforestation hotspot, rampant cropland and pasture expansion raise concerns about the ...sustainability of these land-use changes. Zoning policies were recently enacted in the Argentine Chaco to balance agriculture and conservation, yet the environmental outcomes of implementing these policies remain unclear. Here, we focused on the province of Formosa (Argentina) to evaluate how fully implementing zoning there would affect forest loss and connectivity, and how multiscale landscape planning could enhance environmental outcomes. Specifically, we simulated potential future forest cover for different spatial planning scenarios to assess the effect of (a) implementing regional corridors and (b) enacting additional policies to minimize forest fragmentation at the plot level, under both high and low deforestation rates. We then quantified forest connectivity and fragmentation using morphological image segmentation and landscape indices. Our results show that implementing regional corridors reduced the extent of potential deforestation by 650,000 ha (43%), and this alone strongly increased forest connectivity compared with scenarios without corridors. However, how deforestation would be carried out at the plot level was critically important. Plot-level spatial planning could have a strong and positive effect on mitigating fragmentation and on maintaining connectivity, even in scenarios with high deforestation rates (i.e., reducing the number of forest fragments by up to 35%, increasing the core forest by up to 6%). Moreover, under high deforestation rates, implementing regional corridors and plot-level design had a strong complementary effect on mitigating forest fragmentation (17% less forest fragments than when implementing either of the two strategies alone). Our analyses clearly highlight the opportunities of multiscale spatial planning and the need to complement broad-scale zoning with plot-level landscape design in order to mitigate the negative impacts of deforestation in the Chaco and other active agricultural frontiers.
Context
Land-use change is the main driver of habitat loss and fragmentation worldwide. The rate of dry forest loss in the South American Chaco is among the highest in the world, mainly due to the ...expansion of soybean production and cattle ranching. Argentina recently implemented a national zoning plan (i.e., the Forest Law) to reduce further forest loss. However, it is unclear how the effects of past deforestation and the implementation of the Forest Law will affect forest connectivity in the Chaco.
Objective
Our main goal was to evaluate the potential effect of the Forest Law on forest fragmentation and connectivity in the Argentine Chaco.
Methods
We studied changes in the extent, fragmentation, and connectivity of forests between 1977 and 2010, by combining agricultural expansion and forest cover maps, and for the future in a scenario analysis.
Results
Past agricultural expansion translated into an overall loss of 22.5 % of the Argentine Chaco’s forests, with deforestation rates in 2000–2010 up to three times higher than in the 1980s. Forest fragmentation and connectivity loss were highest in 1977–1992, when road construction fragmented large forest patches. Our future scenario analysis showed that if the Forest Law will be implemented as planned, forest area and connectivity in the region will decline drastically.
Conclusions
Land-use planning designed to protect stepping stones could substantially mitigate connectivity loss due to deforestation, with the co-benefit of preserving the greatest amount of biodiversity priority areas across all evaluated scenarios. Including scenario analyses that assess forest fragmentation and connectivity at the ecoregion scale is thus important in upcoming revisions of the Argentine Forest Law, and, more generally, in debates about sustainable resource use.
Forest conservation Kuemmerle, Tobias; Altrichter, Mariana; Baldi, Germán ...
Science (American Association for the Advancement of Science),
02/2017, Letnik:
355, Številka:
6324
Journal Article
Agricultural expansion is the primary cause of forest loss and fragmentation. It threatens the conservation of its biodiversity as well as the capability to provide ecosystem services. Land-use ...policies, such as zonation programs, have been traditionally used as a tool for promoting a sustainable natural resource management; however, we still lack standardized methodologies that can be applied world-widely to achieve this purpose. In the current context of rampant deforestation over the tropical forests, there is an urgent need of identifying policies that steer agricultural land-use change into a reduced pressure on forests. This study focuses on the outcomes of the first territorial planning law in the Province of Formosa (Argentina) located within the Chaco region, one of the world’s deforestation hotspots. The research questions were: a) How did agriculture expand in Formosa before, during and after the enactment of the territorial planning law? b) Did the introduction of the law affect the spatial distribution of land-use change?; and c) How did the sanction of the law affect forest loss and forest fragmentation? Landsat imagery was used to map land-use change, and to calculate the cover loss and cover loss rate considering the zoning and physiognomic classification of the law. The forest fragmentation was evaluated in terms of forest loss spatial configuration, classified as perforation or shrinkage, forest edge generation, patch size distribution, and patch isolation. The territorial planning law effect over agricultural expansion was tested using a difference in difference model. After the law was passed, a reduced land-use pressure was observed for the forest within the conservation designated zone; however, the forest presented the highest cover loss rates among the physiognomic categories of the law. Land-use change within the conservation designated zone was predominantly made according to a perforation spatial configuration, which promoted the forest edge generation. The isolation between forest patches decreased and its size distribution changed towards a less large-patch-centered pattern, indicating that Formosa is experiencing an early fragmentation process. Overall, the territorial planning law in Formosa succeeded in the relief of land-use pressure on forest, but highlighted the need of incorporating spatial configuration guidelines for long-term forest conservation. The case of Formosa case could be useful in the design of future sustainable natural resource management policies and implies the importance of early natural resource planning.
In forestry, aerial photogrammetry by means of Unmanned Aerial Systems (UAS) could bridge the gap between detailed fieldwork and broad-range satellite imagery-based analysis. However, optical sensors ...are only poorly capable of penetrating the tree canopy, causing raw image-based point clouds unable to reliably collect and classify ground points in woodlands, which is essential for further data processing. In this work, we propose a novel method to overcome this issue and generate accurate a Digital Terrain Model (DTM) in forested environments by processing the point cloud. We also developed a highly realistic custom simulator that allows controlled experimentation with repeatability guaranteed. With this tool, we performed an exhaustive evaluation of the survey and sensor settings and their impact on the 3D reconstruction. Overall, we found that a high frontal overlap (95%), a nadir camera angle (90°), and low flight altitudes (less than 100 m) results in the best configuration for forest environments. We validated the presented method for DTM generation in a simulated and real-world survey missions with both fixed-wing and multicopter UAS, showing how the problem of structural forest parameters estimation can be better addressed. Finally, we applied our method for automatic detection of selective logging.
The forest in the Central Argentine Chaco has been dramatically fragmented and persists only as isolated patches in an agricultural matrix. In this study, we evaluated the effects of fragmentation on ...total density, recruitment, and size-class structure of its dominant tree species, a key issue, although little explored, for forest conservation in the region. We particularly analyzed the effects of fragment size and forest cover at landscape level on seven of the most important tree species of the forest. Our results suggest that forest cover at landscape level is more important than fragment size to explain the population patterns of the main tree species. Fragment size was relevant in only one species, Cordia americana, whereas forest cover resulted relevant in five species. The size-class structure of Schinopsis balansae, one of the dominant species of the upper stratum, appeared to be affected in landscapes with less forest cover, showing lower densities of the smaller classes. Our results show that for the conservation of the forest it would be important to increase their protection degree against the expansion of agriculture, attempting to preserve as much of the forest as possible, to promote the forest cover at landscape level and give relevance even to the smallest fragments.
El bosque de tres quebrachos en el SO de la Provincia de Chaco es un tipo de bosque poco estudiado y muy afectado por la expansión agropecuaria. Se estudió la composición, la estructura y el estado ...de conservación de la comunidad de plantas leñosas de los fragmentos remanentes. A partir de 60 parcelas distribuidas en 16 fragmentos (entre 5 y >1000 ha) se determinó la riqueza y la composición específica de la comunidad y el área basal y la densidad de cada una de las especies. Se detectaron 36 especies leñosas, todas ellas nativas, con un área basal de 24.73 m²/ha y una densidad de 13459 individuos/ha. Entre las especies del estrato superior se encontró una codominancia entre Schinopsis balansae y Aspidosperma quebracho blanco. Para evaluar el estado de conservación se compararon los resultados obtenidos con datos publicados para quebrachales en áreas protegidas de otras subregiones del Chaco argentino. Se encontró una notable similitud tanto en la riqueza como en los parámetros estructurales. El análisis de los tocones sugiere que la extracción selectiva no es de gran intensidad. Estas observaciones reflejarían un estado de conservación del bosque de tres quebrachos que resulta sorprendentemente bueno si se tiene en cuenta su alto grado de fragmentación.
Agricultural expansion threatens biodiversity due to habitat loss and fragmentation. In the Gran Chaco, a global deforestation hotspot, rampant cropland and pasture expansion raise concerns about the ...sustainability of these land-use changes. Zoning policies were recently enacted in the Argentine Chaco to balance agriculture and conservation, yet the environmental outcomes of implementing these policies remain unclear. Here, we focused on the province of Formosa (Argentina) to evaluate how fully implementing zoning there would affect forest loss and connectivity, and how multiscale landscape planning could enhance environmental outcomes. Specifically, we simulated potential future forest cover for different spatial planning scenarios to assess the effect of (a) implementing regional corridors and (b) enacting additional policies to minimize forest fragmentation at the plot level, under both high and low deforestation rates. We then quantified forest connectivity and fragmentation using morphological image segmentation and landscape indices. Our results show that implementing regional corridors reduced the extent of potential deforestation by 650,000 ha (43%), and this alone strongly increased forest connectivity compared with scenarios without corridors. However, how deforestation would be carried out at the plot level was critically important. Plot-level spatial planning could have a strong and positive effect on mitigating fragmentation and on maintaining connectivity, even in scenarios with high deforestation rates (i.e., reducing the number of forest fragments by up to 35%, increasing the core forest by up to 6%). Moreover, under high deforestation rates, implementing regional corridors and plot-level design had a strong complementary effect on mitigating forest fragmentation (17% less forest fragments than when implementing either of the two strategies alone). Our analyses clearly highlight the opportunities of multiscale spatial planning and the need to complement broad-scale zoning with plot-level landscape design in order to mitigate the negative impacts of deforestation in the Chaco and other active agricultural frontiers.
The evolution of total ozone and surface UV radiation over some stations in the southern region of South America and in Antarctica in relationship with polar vortex occurrences is analyzed using ...Total Ozone Mapping Spectrometer total ozone measurements and local surface UV data for the 1997–2003 period. The data are classified as a function of the position of the stations with respect to the polar vortex using equivalent latitude at 550 K isentropic level. The study of vortex occurrences showed that Ushuaia station (54.9°S) was located ∼40% of the cases in the edge of the vortex and 5% inside the vortex core during the winter‐spring period. Concerning the Marambio (62.2°S) and Dumont d'Urville (66.4°S) stations, located on the shore of the Antarctic continent, the analysis shows a zonal asymmetry with respect to the center of the vortex. Marambio is located around 60% of the time inside the vortex, while Dumont d'Urville is predominantly at the edge of or outside the vortex. The evolution of the equivalent latitude of the stations in the anomalous 2002 winter presents a different behavior with respect to other years in the 1997–2003 period. The persistence of the vortex core above the stations is in average 1.8 days over Ushuaia and 7.1 days over Marambio in October during the 1997–2003 period with corresponding mean total ozone columns of 208.2 and 181.4 Dobson units, respectively. When the stations are inside the vortex, the total ozone columns are generally larger at Ushuaia than at Marambio in October during the 1997–2003 period. Finally, the impact of ozone‐depleted air mass occurrences on ultraviolet radiation is evaluated by relating total ozone and UV erythemal dose measured at the stations. Twofold or threefold UV dose increases were reached in the 55°–65° southern latitude region during vortex overpasses, reaching maximum UV dose around 5 kJ/m2. The average increase of UV dose could be computed at the stations considered in the study when the measurement sampling and the number of vortex occurrences was sufficient. An average increase of 67.6% of the erythemal UV dose was found in October at Ushuaia over the years 1997, 1998, and 2000. This value is strongly weighted by vortex occurrences over the station in 2000. At Marambio an average UV increase of 47.4% was found over the years 1999 and 2000. Midlatitude stations like Comodoro Rivadavia (45.8°S) are generally little affected by vortex intrusions. Nevertheless, the maximum UV dose can increase by more than 50% when the vortex passes over the station.
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