We explore the issues relevant to those types of ecosystems containing new combinations of species that arise through human action, environmental change, and the impacts of the deliberate and inadvertent introduction of species from other regions. Novel ecosystems (also termed 'emerging ecosystems') result when species occur in combinations and relative abundances that have not occurred previously within a given biome. Key characteristics are novelty, in the form of new species combinations and the potential for changes in ecosystem functioning, and human agency, in that these ecosystems are the result of deliberate or inadvertent human action. As more of the Earth becomes transformed by human actions, novel ecosystems increase in importance, but are relatively little studied. Either the degradation or invasion of native or 'wild' ecosystems or the abandonment of intensively managed systems can result in the formation of these novel systems. Important considerations are whether these new systems are persistent and what values they may have. It is likely that it may be very difficult or costly to return such systems to their previous state, and hence consideration needs to be given to developing appropriate management goals and approaches.
The Cerrado is one of the world's biodiversity hotspots. In the last 35 years, more than 50% of its approximately 2 million km 2 has been transformed into pasture and agricultural lands planted in cash crops. The Cerrado has the richest flora among the world's savannas (>7000 species) and high levels of endemism. Species richness of birds, fishes, reptiles, amphibians, and insects is equally high, whereas mammal diversity is relatively low. Deforestation rates have been higher in the Cerrado than in the Amazon rainforest, and conservation efforts have been modest: only 2.2% of its area is under legal protection. Numerous animal and plant species are threatened with extinction, and an estimated 20% of threatened and endemic species do not occur in protected areas. Soil erosion, the degradation of the diverse Cerrado vegetation formations, and the spread of exotic grasses are widespread and major threats. The use of fire for clearing land and to encourage new growth for pasture has also caused damage, even though the Cerrado is a fire-adapted ecosystem. Ecosystem experiments and modeling show that change in land cover is altering the hydrology and affecting carbon stocks and fluxes. Cerrado agriculture is lucrative, and agricultural expansion is expected to continue, requiring improvements in and extension of the transportation infrastructure, which will affect not only the Cerrado but also the Amazon forest. Large-scale landscape modification and threats to numerous species have led to renewed interest from various sectors in promoting the conservation of the Cerrado, particularly through strengthening and enlarging the system of protected areas and improving farming practices and thus the livelihoods of local communities. Conservación del Cerrado BrasileñoResumen: El Cerrado es uno de los sitios de importancia para la biodiversidad global. En losúltimos 35 años, más de 50% de sus aproximadamente 2 millones de km 2 ha sido transformado en tierras agrícolas con cultivos comerciales y de pastoreo. El Cerrado tiene la flora más rica entre las sabanas del mundo (>7000 especies) y altos niveles de endemismo. La riqueza de especies de aves, peces, reptiles, anfibios e insectos es igualmente alta, mientras que la diversidad de mamíferos es relativamente baja. Las tasas de deforestación han sido mayores en el Cerrado que en la selva lluviosa del Amazonas, y los esfuerzos de conservación han sido modestos: solo 2.2% de su superficie esta legalmente protegido. Numerosas especies de animales y plantas están amenazadas de extinción, y se estima que 20% de las especies amenazadas y endémicas no existen enáreas protegidas. La erosión del suelo, la degradación de diversas formaciones vegetales y la expansión de pastos exóticos son las amenazas principales y generalizadas. El uso de fuego para desmontar terrenos y estimular pastura nueva también ha causado daño, a pesar de que el Cerrado es un ecosistema adaptado al fuego. Experimentos y modelos del ecosistema muestran que el cambio en la cobertura del suelo esta alterando la hid...
Aim This paper presents a spatial classification of the environmental and ecological diversity of the cerrado region of Brazil, as well as an appraisal of the levels of conversion to agriculture and of the extent of land protection.Location The cerrado region of Brazil, located in the centre of Brazil, occupies c. 2.5 million square kilometres. Our study area represents roughly 85% of the total. This ecologically heterogeneous region is dominated by savannas, but also contains several types of forests and xerophytic communities that often form mosaics with the savannas. Its high biodiversity is seriously threatened by the accelerated process of conversion to agriculture and a deficiency in the extent and the representativeness of protected areas.Methods We selected 124 land systems from a previous study of the lowlands of South America. The maps were digitized and 41 parameters, where environmental information was available, were used to build a matrix. A cluster analysis was then performed and the results used to classify the land systems into units at two scales. The larger units, characterized by the dominant landform and vegetation, were considered as landscape units. Within each of these, smaller units called ecological units were defined by the physiognomy and phenology of the dominant vegetation, topography and drainage. Using GIS, we mapped the resulting ecological units and incorporated the information on land use from the municipal agricultural census of 1996. In addition, data on the extent of protected land units was used to assess the status of land protection in each ecological unit.Results Five landscape units and 15 ecological units were identified, mapped and explained. These units were not continuous but were represented by disjunct patches located in different parts of the study region. Brief descriptions are given including the geographical locations and dominant ecological features. They also include the extent of land conversion to agriculture (1996 census figures) in each of the various patches as well as the number and area of units of conservation. Main conclusionsThe high level of land conversion to agriculture is a major threat to the conservation of the remarkable biodiversity of the cerrado region. This, together with the poor status of land protection, represents the major environmental problem facing this region. However, the fact that areas with similar general ecological conditions have a disjunct distribution is important for conservation purposes, even though the details of floristic similarities and biogeographic influences have still to be worked out. Our detailed spatial classification has made this disjunction clearly apparent and has allowed us to map ecologically similar areas accurately. This allows the evaluation of the status of these areas in terms of land use and land protection and may be used in the design of conservation strategies.
Summary 1.Water is a key resource in tropical savannas. Changes in vegetation structure due to land-use change and increased fire frequency may affect the availability of water and the flux of water through these ecosystems. 2. We compared the seasonal soil moisture dynamics of two adjacent savanna ecosystems with contrasting tree densities in central Brazil. Our goal was to investigate the influence of tree density on deep water uptake, soil water dynamics and evapotranspiration. 3. Soil water was measured using a depth of 7·5 m beneath the tree-dominated cerrado denso ecosystem and to 4 m beneath the grass-dominated campo sujo ecosystem. Plantavailable water (PAW) throughout the cerrado denso soil profile ranged from 293 mm at the end of the dry season to 689 mm during the wet season. In the grass-dominated site, PAW in the profile ranged from 155 to 362 mm. 4. During the dry season, ≈ 82% of the water used in cerrado denso and 67% in campo sujo was extracted from the profile below 1 m. The tree-dominated cerrado denso used 137 mm more water than the grass-dominated campo sujo . Significant deep soil water uptake was also observed during the wet season of 1998, when rainfall was below average. 5. Evapotranspiration (ET) rates (estimated as change in soil moisture over time) were higher in cerrado denso than in campo sujo during both seasons. Estimated ET ranged from 1·4 mm day − 1 during the dry season to 5·8 mm day − 1 for the wet season in cerrado denso , and from 0·9 mm day − 1 in the dry season to 4·5 mm day − 1 in early wet season in campo sujo . The differences in PAW and ET rates between the two ecosystems are associated not only with differences in root distribution, but also with differences in tree densities and the phenology of full-leaf canopies. 6. Our results suggest that deep-rooted plants may contribute significantly to the water balance of cerrado ecosystems, and that the hydrological cycle of this biome could change as woody vegetation is replaced by exotic grasses and agricultural crops.
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