The present conservation status of Juniperus forests in the South Ethiopian Endemic Bird Area

Field survey data and Landsat satellite imagery were used to evaluate the conservation status of two Juniperus forests (Mankubsa and Arero) in the south Ethiopian Endemic Bird Area. Forest cover and dense woodland decreased in both areas between 1986 and 2002, but rates of habitat change and human impact were greater at Mankubsa than at Arero. We suggest that at Mankubsa increased grazing pressure, agricultural expansion, commercial fuelwood and timber exploitation are threatening forest persistence, while most of the degradation at Arero is because of the grazing of domestic animals. Conservation efforts should focus on creating tree plantations and improving forest resource use efficiency at Mankubsa, while at Arero better results could be obtained by improving pasture quality in the habitats surrounding the forest.     

Integration of remote sensing techniques for monitoring desertification in Mexico

Desertification is considered one of the most serious threats to arid, semiarid, and sub-humid environments. In this study, several remote sensing techniques were integrated for monitoring desertification in a semiarid region of the central Mexican plateau (state of Querétaro). Landsat TM images were used to compute the Normalized Difference Vegetation Index (NDVI), Bare-Soil Index (BSI), and albedo (α). A change vector analysis (CVA) examined changes in the direction and magnitude of indicators during the 1993–2011 period in order to detect degradations or improvements in land conditions over a period of time. In addition, a desertification degree index (DDI) was applied based on the NDVI–α relationship. The results indicated that in the semiarid zone of the state of Querétaro, 48.3% of land use corresponds with agricultural areas; 2.7% of the area does not present any degree of desertification, while 49% presents the following degrees of desertification: 5.5% extreme, 10.9% severe, 18.9% moderate, and 13.7% low. The DDI applied in this approach for evaluating this phenomenon at the regional and municipal level is an effective tool for identifying areas at risk of desertification, in addition to monitoring changes in the degree or direction of desertification.     

Satellite remote sensing of freshwater macrophytes and the influence of water clarity

In regions with thousands of lakes, large scale regional macrophyte surveys are rarely done due to logistical difficulties and high costs. We examined whether remote sensing can be used for regional monitoring of macrophytes in inland lakes using a field study of 13 lakes in Michigan, USA (nine model development lakes and four model testing lakes). Our objectives were: (1) to determine if different levels of macrophyte cover, different growth forms or specific species could be detected using the Landsat-5 TM sensor, and (2) to determine if we could improve predictions of macrophyte abundance and distribution in lakes by including sediment type or measures of water clarity (Secchi disk transparency, chlorophyll a, phytoplankton biovolume, or water color) in our models. Using binomial and multinomial logistic regression models, we found statistically significant relationships between most macrophyte measures and Landsat-5 TM values in the nine model development lakes (percent concordant values: 58–97%). Additionally, we found significant correlations between three lake characteristics and the TM values within lake pelagic zones, despite the inability of these variables to improve model predictions. However, model validation using four lakes was generally low, suggesting caution in applying these models to other lakes. Although the initial model development results suggest that remote sensing is a potentially promising tool for regionally assessing macrophytes, more research is necessary to refine the models in order for them to be applied to unsampled lakes.     

Spatial and temporal deforestation dynamics in protected and unprotected dry forests: a case study from Myanmar (Burma)

Tropical dry forests are more threatened, less protected and especially susceptible to deforestation. However, most deforestation research focuses on tropical rain forests. We analyzed spatial and temporal changes in land cover from 1972 through 2005 at Chatthin Wildlife Sanctuary (CWS), a tropical dry forest in Myanmar (Burma). CWS is one of the largest protected patches of tropical dry forest in Southeast Asia and supports over half the remaining wild population of the endangered Eld’s deer. Between 1973 and 2005, 62% of forest was lost at an annual rate of 1.86% in the area, while forest loss inside CWS was only 16% (0.45% annually). Based on trends found during our study period, dry forests outside CWS would not persist beyond 2019, while forests inside CWS would persist for at least another 100 years. Analysis of temporal deforestation patterns indicates the highest rate of loss occurred between 1992 and 2001. Conversion to agriculture, shifting agriculture, and flooding from a hydro-electric development were the main deforestation drivers. Fragmentation was also severe, halving the area of suitable Eld’s deer habitat between 1973 and 2001, and increasing its isolation. CWS protection efforts were effective in reducing deforestation rates, although deforestation effects extended up to 2 km into the sanctuary. Establishing new protected areas for dry forests and finding ways to mitigate human impacts on existing forests are both needed to protect remaining dry forests and the species they support.     

The riverscape of Western Amazonia – a quantitative approach to the fluvial biogeography of the region

Aim To provide a quantitative spatial analysis of the riverscape (open‐water bodies and their surrounding areas) of the Western Amazonian lowlands using a consistent surface of remotely sensed imagery. Taking into account the essential significance of fluvial environments for the Amazonian biota, we propose that an enhanced understanding of the Amazonian riverscape will provide new insight for biogeographical studies in the region and contribute to the understanding of these megadiverse tropical lowlands. Location An area of 2.2 million km² covering the Western Amazonian lowlands of the Andean foreland region, i.e. the upper reaches of the Amazon river system. Areas in Colombia, Venezuela, Ecuador, Peru, Brazil and Bolivia between longitudes 83 °W and 65 °W and latitudes 5 °N and 12 °S are included. Methods A mosaic of 120 Landsat TM satellite images was created with 100‐m resolution, and water areas of over 1 ha in size or c. 60 m in width were extracted using a simple ratio threshold applicable to a large set of data. With this method, 99.1% of the water areas present in 30‐m imagery were mapped with images with 100‐m resolution. Water pixels of distinct river segments were assigned to river classes on the basis of their channel properties, and islands and lakes were distinguished separately and classified. Measures of water patterns such as structure, composition, richness and remoteness were provided for various spatial units. Riverine corridors were computed from the open‐water mask by outer limits of active channels and floodplain lakes. Analytical results are shown as both thematic maps and statistics. Results A total of 1.1% of Western Amazonia is covered by open‐water bodies over 1 ha in size or 60 m in width. River‐bound waters comprise 98% of the total water surface. Whilst isolated lakes are scarce, river‐bound oxbow and backchannel lakes are plentiful, comprising 17.5% of all waters. They are particularly frequent along meandering channels, which dominate both in area and length. The riverine corridors including active channels and floodplain lakes cover 17% of the land area. The average distance from any point of land to the nearest water is 12 km. Geographically speaking, the distribution of waters is uneven across the region, and the detailed characteristics of the riverscape are geographically highly variable. Three major, fluvially distinct regions can be identified: central Western Amazonia, the south, and the north‐east. The proportional surface areas of the riverine corridors, numbers of lakes, sizes of islands and their distributions depend largely on the types and sizes of the rivers. Main conclusions Our results support the notion of Western Amazonia as a dynamic, highly fluvial environment, highlighting and quantifying considerable internal variation within the region in terms of fluvial patterns and the processes that they reflect and control. Biogeographically, the variety of types of fluvial environments and their characteristics are important constituents of what influences the distribution of species and dynamics of terrestrial habitats. Spatially consistent riverscape data can serve as a consistent and scalable source of relevant information for other biogeographical approaches in the region.     

Habitat Use and Ranging of Wild Bonobos (Pan paniscus) at Wamba

The relationship between vegetation and ranging patterns of wild bonobos at Wamba, Democratic Republic of the Congo, was examined. Via Landsat data, we distinguished three types of vegetation—dry forest, swamp forest, and disturbed forest—at Wamba. The home ranges of the study groups changed considerably from year to year, due mainly to intergroup relationships. The population density of each group varied between 1.4 and 2.5 individuals per km ² and was lowest during a period of population increase. Home ranges consisted mainly of dry forest. The bonobos used dry forest more frequently than the other forest types, though they also used swamp and disturbed forest almost every day. The latter types of forest seemed to be important resources for the bonobos, owing to the abundant herbaceous plants that are rich in protein and constantly available. The bonobos tended to use dry forest more frequently in the rainy season than in the relatively dry season, probably because the favored fruits in the dry forest were mostly available in the rainy season. There was no seasonal difference in the size of the daily ranging area.     

Possible implications of the oceanographic thermal effects in a landsat infrared imagery of Mauritius

Sea surface temperature (SST) and inland thermal effects were sensed by the thermal infrared channel 6 of the Landsat 4 Thematic Mapper on a special acquisition scene of Mauritius. Contrary to the general belief, the lagoon waters appeared colder than the open oceanic water. This surprising discovery would appear to indicate that cold, high altitude inland water reaching the lagoons produces the effect. In the absence of supportive evidence, the biological consequences of this natural phenomenon can only be speculated. However, this interpretation can be substantiated by in situ measurements of SST from boats.On a larger scale, the channel 6 of Landsat 4 TM showed blovs of warm oceanic white water which appeared to be drifting past the island landmass. The suggestion that this effect could be due to the release of heated waste water from coastal sources was eventually ruled out by closer analysis of the image. The nature of the phenomenon is not known. High reflectance due to backscattering of light by blooming phytoplankton could be a possible cause, but this could similarly be resolved by measurements of SST from ship cruises, analyses of offshore water samples and by the use of NOAA AVHRR data.     

A vegetation-based method to map climatic variation in the arctic–boreal transition area of Finnmark, north-easternmost Norway

Aim To develop a new method for bioclimate mapping where the vegetation layer is the main source of climate information. Location The study area includes four subareas, all situated on the Varangerhalvøya peninsula in Finnmark, north‐easternmost Norway (70–71° N). The four subareas were chosen to represent most of the climatic, topographic, geomorphologic and botanic diversity along the arctic–boreal gradient in the area. The four meteorological stations in the area show a climatic gradient with mean July temperature ranging from 10.1 to 12.3 °C. Methods The new vegetation‐based method is based on the fact that most plant species and plant communities both in the Arctic and adjacent areas have a distribution pattern limited by temperature to some extent. The vegetation is mapped using Landsat TM data and a contextual correction process in a geographic information system. The mapped vegetation units are defined as temperature indicators based on their total distribution patterns and the temperature indicator value of their high frequency and dominant species. The indicator value and degree of cover of all thermophilous vegetation units, within each 500 × 500 m study unit, are combined in a Vegetation‐based Index of Thermophily, VI_tm. This new vegetation‐based method is based on the same basic idea as a recently published floristic‐based method for calculating a Floristic‐based Index of Thermophily, FI_tm. The VI_tm values are tested by comparison with the FI_tm values, and temperature data collected in the field during two growing seasons, and the differences are interpreted ecologically. Results Twenty‐one of the mapped vegetation units were defined as thermophilous and categorized in five groups of temperature indicators. The VI_tm values showed a strong positive linear relationship with the temperatures measured during the years 2001 and 2002, with r² values of 0.79 and 0.85, respectively. The VI_tm values show a high linear relationship (r² = 0.76) with the 71 study units where the FI_tm values were calculated. As interpreted from the relationship with temperature measurements and FI_tm values, the vegetation‐based method seems to work at a broad range of ecological conditions, with very dry, acidic sites being the most important exception. The VI_tm values are related to growing degree‐days of a normal year, and the four subareas are mapped, showing a diversity of 13 bioclimatic classes. The birch forest line is estimated to occur at about 980 °C‐days. The results show climatic gradients with temperatures increasing from the cold coast towards the interior, from wind‐exposed convex hills towards wind‐protected valleys, and from mountain plateaux towards south‐facing lowlands. The north‐easternmost study site at the coast is positioned within the arctic shrub tundra zone. Main conclusions The vegetation‐based method shows a strong positive correlation both with measured temperatures and the floristic‐based method within a broad range of different ecological conditions. The vegetation‐based method has the potential for bioclimatic mapping of large areas in a cost‐effective way. The floristic‐based method has higher accuracy and is more flexible than the vegetation‐based method, and the two methods seem to complement each other.