首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 34 毫秒
1.
Agricultural expansion is a leading driver of biodiversity loss across the world, but little is known on how future land‐use change may encroach on remaining natural vegetation. This uncertainty is, in part, due to unknown levels of future agricultural intensification and international trade. Using an economic land‐use model, we assessed potential future losses of natural vegetation with a focus on how these may threaten biodiversity hotspots and intact forest landscapes. We analysed agricultural expansion under proactive and reactive biodiversity protection scenarios, and for different rates of pasture intensification. We found growing food demand to lead to a significant expansion of cropland at the expense of pastures and natural vegetation. In our reference scenario, global cropland area increased by more than 400 Mha between 2015 and 2050, mostly in Africa and Latin America. Grazing intensification was a main determinant of future land‐use change. In Africa, higher rates of pasture intensification resulted in smaller losses of natural vegetation, and reduced pressure on biodiversity hotspots and intact forest landscapes. Investments into raising pasture productivity in conjunction with proactive land‐use planning appear essential in Africa to reduce further losses of areas with high conservation value. In Latin America, in contrast, higher pasture productivity resulted in increased livestock exports, highlighting that unchecked trade can reduce the land savings of pasture intensification. Reactive protection of sensitive areas significantly reduced the conversion of natural ecosystems in Latin America. We conclude that protection strategies need to adapt to region‐specific trade positions. In regions with a high involvement in international trade, area‐based conservation measures should be preferred over strategies aimed at increasing pasture productivity, which by themselves might not be sufficient to protect biodiversity effectively.  相似文献   

2.
This article attempts to conceptualize the dynamics of resource allocation by colonist farmers under the unique conditions of land abundance and labor scarcity which characterize frontier environments, such as the smallholder agricultural settlement areas in the Amazon basin. In contrast, most previous theoretical literature on household agricultural decision making and land-use change in rural areas considers conditions of high population density and land scarcity, and is not, therefore, adequate for understanding critical land-use changes which may be occurring in frontier regions. This article first discusses the appropriateness and inadequacies of the analytical frameworks commonly used to explain the expansion of settler agriculture into remote forest regions and the unsustainable land-use practices observed in these areas. This review serves as the basis for characterizing resource allocation under the particular conditions of frontier environments. A conceptual advance in the analysis is its consideration of the way institutional/policy factors and farm-level characteristics can interact to produce land-use outcomes. This knowledge is essential to understand not only the social and economic factors affecting present land use and choice of technology, but also those factors influencing farmers' demand for more optimal systems of land use which are consistent with varying agro-ecological potentials, demographic situations, and their own management capacity.  相似文献   

3.
Land-use intensification is a central element in proposed strategies to address global food security. One rationale for accepting the negative consequences of land-use intensification for farmland biodiversity is that it could ‘spare’ further expansion of agriculture into remaining natural habitats. However, in many regions of the world the only natural habitats that can be spared are fragments within landscapes dominated by agriculture. Therefore, land-sparing arguments hinge on land-use intensification having low spillover effects into adjacent protected areas, otherwise net conservation gains will diminish with increasing intensification. We test, for the first time, whether the degree of spillover from farmland into adjacent natural habitats scales in magnitude with increasing land-use intensity. We identified a continuous land-use intensity gradient across pastoral farming systems in New Zealand (based on 13 components of farmer input and soil biogeochemistry variables), and measured cumulative off-site spillover effects of fertilisers and livestock on soil biogeochemistry in 21 adjacent forest remnants. Ten of 11 measured soil properties differed significantly between remnants and intact-forest reference sites, for both fenced and unfenced remnants, at both edge and interior. For seven variables, the magnitude of effects scaled significantly with magnitude of surrounding land-use intensity, through complex interactions with fencing and edge effects. In particular, total C, total N, δ15N, total P and heavy-metal contaminants of phosphate fertilizers (Cd and U) increased significantly within remnants in response to increasing land-use intensity, and these effects were exacerbated in unfenced relative to fenced remnants. This suggests movement of livestock into surrounding natural habitats is a significant component of agricultural spillover, but pervasive changes in soil biogeochemistry still occur through nutrient spillover channels alone, even in fenced remnants set aside for conservation. These results have important implications for the viability of land-sparing as a strategy for balancing landscape-level conservation and production goals in agricultural landscapes.  相似文献   

4.
Since the 1970s the Brazilian Amazon has received over 1 million migrant farm households from other regions of the country, many of whom were attracted to government-sponsored frontier settlement programs that offered free tropical forest land. As a result, pressures on tropical forests have intensified along several settlement corridors throughout the region. Despite their importance as agents of landscape change, surprisingly little is known about the land use practices of these farmers. This paper briefly reviews the research literature on smallholder land use patterns in Amazonia, describes the recent history of one important agricultural land settlement program in the western Brazilian Amazon state of Rondônia, and, based on 240 household surveys conducted in three separate settlement locations in the state, highlights key differences in land use patterns among the rural population. Typologies of farming systems are presented on the basis of cluster analysis of land use data and ANOVA tests. The findings indicate considerable complexity and heterogeneity in smallholder farming systems. Spatial variations in farming system types may be due to geographic differences in soil regimes, the social histories of specific communities, and site-specific responses to exogenous variables.  相似文献   

5.
Swidden agriculture, commercial logging and plantation development have been considered to be the primary common causes of degradation and loss of tropical rain forests in Southeast Asia. In this paper, I chose a part of northeastern Sarawak, East Malaysia as my case study area to analyze the changes in its land-use characteristics. In the study area, as well as primeval forests, we see that land use began about 100 years ago by a native group called the Iban; commercial logging began in the 1960s, and the development of oil palm plantations began recently. I describe the changes in land use as well as their social and economic causes by referring to aerial photographs, literature surveys, interviews with government officers and the Iban, and observation of land use. My analysis of land use demonstrates that on “state land”, where commercial logging and oil palm plantation development are occurring, large areas of forest have been disturbed in a short period of time. The objective is to benefit economically in response to the social and economic conditions surrounding the study area. On the other hand, in the “Iban territory,” where the Iban practice their land use, land conversion has not occurred on a large scale and in a short period of time, even though the forest has been cut and agricultural fields have been created in response to social and economic conditions as well. They disperse small agricultural fields throughout their forest land. Therefore, the landscape of the “Iban territory” is based on secondary forest, composed of patches of forest in various stages and with several types of agricultural land. Today in Sarawak, monocrop plantations are rapidly expanding and little primeval forest remains. Given these conditions, the land-use practices of natives such as the Iban will be evaluated from the viewpoint of ecosystem and biodiversity conservation. It could play an important role in providing habitats for natural wildlife.  相似文献   

6.
The imminence of forest conversion in the northern Andean region requires a careful evaluation of the social, political and economic context in which environmental efforts take place in order to achieve conservation. Through its socioeconomic effects violent conflict can result in threats pertinent to both conservation and resource management schemes. A survey of the San Lucas mountain range, at the northern tip of the Colombian Central Andes, is presented as a case study of factors associated with violent conflict that may hinder or enhance conservation in this complex social and political setting. Instability in land use and tenure associated with armed conflict were identified as major pressures associated with further conversion of tropical forest habitats; while low rates of settlement and measures enforced by armed rule were very effective in preserving certain tracts of forest. War certainly alleviates demographic pressure from settlers, but contemporary patterns of colonization in San Lucas suggest that armed conflict is detrimental to conservation purposes and to key members of the biological community.  相似文献   

7.
Mexico’s 1992 agrarian counter-reforms opened up the country’s vast network of common property regimes, known as ejidos, to the possibility of privatization. This study investigates the relationship between dynamic common property regimes and deforestation in the wake of policy reform among eight ejidos in southeastern Mexico. Using institutional analyses, land use/land cover change (LULCC) analyses and a Forest Dependency Index, we examine how land tenure arrangements relate to land use and forest cover change patterns. We demonstrate that informally privatized ejidos had larger individual landholdings, more land in use, and higher rates of deforestation. Commonly-held ejidos exhibited lower deforestation rates and, in some cases, forests provided economic benefits via community forest management. However, forest dependency did not correlate with low deforestation rates, suggesting alternative pathways for conservation.  相似文献   

8.
Land‐use change is both a cause and consequence of many biophysical and socioeconomic changes. The CLUMondo model provides an innovative approach for global land‐use change modeling to support integrated assessments. Demands for goods and services are, in the model, supplied by a variety of land systems that are characterized by their land cover mosaic, the agricultural management intensity, and livestock. Land system changes are simulated by the model, driven by regional demand for goods and influenced by local factors that either constrain or promote land system conversion. A characteristic of the new model is the endogenous simulation of intensification of agricultural management versus expansion of arable land, and urban versus rural settlements expansion based on land availability in the neighborhood of the location. Model results for the OECD Environmental Outlook scenario show that allocation of increased agricultural production by either management intensification or area expansion varies both among and within world regions, providing useful insight into the land sparing versus land sharing debate. The land system approach allows the inclusion of different types of demand for goods and services from the land system as a driving factor of land system change. Simulation results are compared to observed changes over the 1970–2000 period and projections of other global and regional land change models.  相似文献   

9.
We evaluated the effects of different land-use systems on the ability of dung beetles to control the population of detritus-feeding flies. We tested the hypotheses that intensification of land use will reduce dung beetles richness, abundance and biomass and, consequently, their dung burial ability, affecting the interaction between dung beetles and flies and reducing its effectiveness as a natural biological control. In the Brazilian Amazon we sampled dung beetles, fly larvae and adults; and recorded the rate of dung removal by dung beetles across a gradient of land-use intensity from primary forest, secondary forest, agroforestry, agriculture to pasture. Our results provide evidence that land-use intensification results in a reduction of the richness, abundance and biomass of dung beetles, and this in turn results in lower rates of dung removal in the most simplified systems. We found no significant differences in the abundance of fly larvae between the different systems of land use. However, the number of adult flies differed significantly between land-use systems, presenting higher abundance in those sites with greater intensity of use (pasture and agriculture) and a lower abundance of adult flies in forested systems (primary and secondary forests, and agroforestry). Information-theoretic model selection based on AICc revealed strong support for the influence of land-use systems, dung removal rates and dung beetle abundance, biomass and richness on adult dung-fly abundance. Our results also reveal that dung beetles are not solely responsible for fly control and that other factors linked to land use are influencing the populations of these detritus-feeding insects.  相似文献   

10.
Closing yield gaps within existing croplands, and thereby avoiding further habitat conversions, is a prominently and controversially discussed strategy to meet the rising demand for agricultural products, while minimizing biodiversity impacts. The agricultural intensification associated with such a strategy poses additional threats to biodiversity within agricultural landscapes. The uneven spatial distribution of both yield gaps and biodiversity provides opportunities for reconciling agricultural intensification and biodiversity conservation through spatially optimized intensification. Here, we integrate distribution and habitat information for almost 20,000 vertebrate species with land‐cover and land‐use datasets. We estimate that projected agricultural intensification between 2000 and 2040 would reduce the global biodiversity value of agricultural lands by 11%, relative to 2000. Contrasting these projections with spatial land‐use optimization scenarios reveals that 88% of projected biodiversity loss could be avoided through globally coordinated land‐use planning, implying huge efficiency gains through international cooperation. However, global‐scale optimization also implies a highly uneven distribution of costs and benefits, resulting in distinct “winners and losers” in terms of national economic development, food security, food sovereignty or conservation. Given conflicting national interests and lacking effective governance mechanisms to guarantee equitable compensation of losers, multinational land‐use optimization seems politically unlikely. In turn, 61% of projected biodiversity loss could be avoided through nationally focused optimization, and 33% through optimization within just 10 countries. Targeted efforts to improve the capacity for integrated land‐use planning for sustainable intensification especially in these countries, including the strengthening of institutions that can arbitrate subnational land‐use conflicts, may offer an effective, yet politically feasible, avenue to better reconcile future trade‐offs between agriculture and conservation. The efficiency gains of optimization remained robust when assuming that yields could only be increased to 80% of their potential. Our results highlight the need to better integrate real‐world governance, political and economic challenges into sustainable development and global change mitigation research.  相似文献   

11.
Carabid beetle assemblages were studied to assess how diversity and community structure varied along a gradient of land-use. This gradient was composed of six 1 km2 quadrats with an increasing proportion of agricultural land reflecting the anthropogenic fragmentation and intensification of landscapes. Carabid species richness and abundance was predicted to peak in the most heterogeneous landscape, in accord with the intermediate disturbance hypothesis (IDH), and then decline as agricultural intensification increased. It was also predicted that the different landscapes would support beetle communities distinct from each other. The IDH was unsupported-in both years of this study carabid species richness and abundance was greatest in the most intensively managed, agricultural sites. Detrended correspondence analysis revealed a clear separation in beetle community structure between forested and open habitats and between different forest types. Canonical correspondence analysis revealed a significant correlation between beetle community structure and the environment, showing distinct beetle assemblages to be significantly associated with specific edaphic and botanical features of the land-use gradient. This study adds to increasing evidence that landscape-scale patterns in land-use significantly affect beetle community structure producing distinct assemblages.  相似文献   

12.
Reconciling the aims of feeding an ever more demanding human population and conserving biodiversity is a difficult challenge. Here, we explore potential solutions by assessing whether land sparing (farming for high yield, potentially enabling the protection of non-farmland habitat), land sharing (lower yielding farming with more biodiversity within farmland) or a mixed strategy would result in better bird conservation outcomes for a specified level of agricultural production. We surveyed forest and farmland study areas in southern Uganda, measuring the population density of 256 bird species and agricultural yield: food energy and gross income. Parametric non-linear functions relating density to yield were fitted. Species were identified as “winners” (total population size always at least as great with agriculture present as without it) or “losers” (total population sometimes or always reduced with agriculture present) for a range of targets for total agricultural production. For each target we determined whether each species would be predicted to have a higher total population with land sparing, land sharing or with any intermediate level of sparing at an intermediate yield. We found that most species were expected to have their highest total populations with land sparing, particularly loser species and species with small global range sizes. Hence, more species would benefit from high-yield farming if used as part of a strategy to reduce forest loss than from low-yield farming and land sharing, as has been found in Ghana and India in a previous study. We caution against advocacy for high-yield farming alone as a means to deliver land sparing if it is done without strong protection for natural habitats, other ecosystem services and social welfare. Instead, we suggest that conservationists explore how conservation and agricultural policies can be better integrated to deliver land sparing by, for example, combining land-use planning and agronomic support for small farmers.  相似文献   

13.
Projection of land use and land-cover change is highly uncertain yet drives critical estimates of carbon emissions, climate change, and food and bioenergy production. We use new, spatially explicit land availability data in conjunction with a model sensitivity analysis to estimate the effects of additional land protection on land use and land cover. The land availability data include protected land and agricultural suitability and is incorporated into the Moirai land data system for initializing the Global Change Analysis Model. Overall, decreasing land availability is relatively inefficient at preserving undeveloped land while having considerable regional land-use impacts. Current amounts of protected area have little effect on land and crop production estimates, but including the spatial distribution of unsuitable (i.e., unavailable) land dramatically shifts bioenergy production from high northern latitudes to the rest of the world, compared with uniform availability. This highlights the importance of spatial heterogeneity in understanding and managing land change. Approximately doubling the current protected area to emulate a 30% protected area target may avoid land conversion by 2050 of less than half the newly protected extent while reducing bioenergy feedstock land by 10.4% and cropland and grazed pasture by over 3%. Regional bioenergy land may be reduced (increased) by up to 46% (36%), cropland reduced by up to 61%, pasture reduced by up to 100%, and harvested forest reduced by up to 35%. Only a few regions show notable gains in some undeveloped land types of up to 36%. Half of the regions can reach the target using only unsuitable land, which would minimize impacts on agriculture but may not meet conservation goals. Rather than focusing on an area target, a more robust approach may be to carefully select newly protected land to meet well-defined conservation goals while minimizing impacts to agriculture.  相似文献   

14.
Habitat loss and degradation, driven largely by agricultural expansion and intensification, present the greatest immediate threat to biodiversity. Tropical forests harbour among the highest levels of terrestrial species diversity and are likely to experience rapid land-use change in the coming decades. Synthetic analyses of observed responses of species are useful for quantifying how land use affects biodiversity and for predicting outcomes under land-use scenarios. Previous applications of this approach have typically focused on individual taxonomic groups, analysing the average response of the whole community to changes in land use. Here, we incorporate quantitative remotely sensed data about habitats in, to our knowledge, the first worldwide synthetic analysis of how individual species in four major taxonomic groups—invertebrates, ‘herptiles’ (reptiles and amphibians), mammals and birds—respond to multiple human pressures in tropical and sub-tropical forests. We show significant independent impacts of land use, human vegetation offtake, forest cover and human population density on both occurrence and abundance of species, highlighting the value of analysing multiple explanatory variables simultaneously. Responses differ among the four groups considered, and—within birds and mammals—between habitat specialists and habitat generalists and between narrow-ranged and wide-ranged species.  相似文献   

15.
Capsule The conservation of Red-backed Shrikes on farmland habitats depends on extensive farming conditions.

Aims To evaluate breeding density and habitat preferences of the declining Red-backed Shrike and relate its occurrence to an environmental gradient ranging from land abandonment to intensive farming.

Methods The study was carried out in the Apennines (northern Italy), at nine 21-ha study plots. We identified factors affecting breeding density and habitat preferences at two spatial scales (landscape and territory) and analysed the variation in territory density according to the relative farming intensity in a low-intensity agricultural landscape.

Results The presence of shrubs and cultivated/grazed land positively influenced the number of Red-backed Shrike territories per plot, while the species' settlement within plots was related to higher values of shrub cover and the presence of hedges. Shrike occurrence was associated with land-use categories intermediate between land abandonment and intensive agriculture.

Conclusions This study provides a first detailed assessment of Red-backed Shrike habitat requirements in southern Europe. Favoured habitats were pasture/cultivation mosaics flanked by or interspersed with shrubs/hedges (15–20% of the surface of the 1-ha medium-sized territory). Thus, the conservation of Red-backed Shrikes in low-intensity southern European farmland appears to reflect a trade-off between agricultural intensification and long-term land abandonment.  相似文献   

16.
A new deforestation and land-use change scenario generator model (FOREST-SAGE) is presented that is designed to interface directly with dynamic vegetation models used in latest generation earth system models. The model requires a regional-scale scenario for aggregate land-use change that may be time-dependent, provided by observational studies or by regional land-use change/economic models for future projections. These land-use categories of the observations/economic model are first translated into equivalent plant function types used by the particular vegetation model, and then FOREST-SAGE disaggregates the regional-scale scenario to the local grid-scale of the earth system model using a set of risk-rules based on factors such as proximity to transport networks, distance weighted population density, forest fragmentation and presence of protected areas and logging concessions. These rules presently focus on the conversion of forest to agriculture and pasture use, but could be generalized to other land use change conversions. After introducing the model, an evaluation of its performance is shown for the land-cover changes that have occurred in the Central African Basin from 2001–2010 using retrievals from MODerate Resolution Imaging Spectroradiometer Vegetation Continuous Field data. The model is able to broadly reproduce the spatial patterns of forest cover change observed by MODIS, and the use of the local-scale risk factors enables FOREST-SAGE to improve land use change patterns considerably relative to benchmark scenarios used in the latest Coupled Model Intercomparison Project integrations. The uncertainty to the various risk factors is investigated using an ensemble of investigations, and it is shown that the model is sensitive to the population density, forest fragmentation and reforestation factors specified.  相似文献   

17.
Land-use intensification in Mediterranean agro-forest systems became a pressure on biodiversity, concerning particularly the woodland sensitive species. In 2001, the effects of a land-use gradient from old-growth cork-oak forest to a homogeneous agricultural area were assessed using rove beetles as indicators in a Mediterranean landscape. The aim was to find which species were negatively affected by land-use intensification at the landscape level and whether they benefited from cork-oak patches occurring along the land-use gradient. A total of 3,196 rove beetles from 88 taxa were sampled from all landscape types. Agricultural area recorded significantly higher numbers of abundance and species richness in relation to the cork-oak mosaics, i.e. the old-growth forest and the managed agro-forest landscapes (montados). Moreover, 70% of rove beetle indicator species common enough to be tested by IndVal displayed their highest indicator value for agriculture, showing a lower number of woodland indicators in comparison to ground beetles. Nevertheless, one rove beetle taxon was considered a specialist of closed woodland mosaics while no specialist ground beetle was found for that landscape typology. Some rare rove beetle species were also important in typifying diversity patterns of old-growth cork-oak forests. Hence, future management in Mediterranean landscapes should take into account not only indicator species common enough to be tested by IndVal, but also rare and endemic species. Considering the added value of cork-oak woodland cover for sensitive rove and ground beetle diversity, the strengthening of cork-oak woodland connectivity seems to be a crucial management that is required in agricultural Mediterranean landscapes.  相似文献   

18.
Brazil is one of the major contributors to land‐use change emissions, mostly driven by agricultural expansion for food, feed, and bioenergy feedstock. Policies to avoid deforestation related to private commitments, economic incentives, and other support schemes are expected to improve the effectiveness of current command and control mechanisms increasingly. However, until recently, land tenure was unknown for much of the Brazilian territory, which has undermined the governance of native vegetation and challenged support and incentive mechanisms for avoiding deforestation. We assess the total extent of public governance mechanisms protecting aboveground carbon (AGC) stocks. We constructed a land tenure dataset for the entire nation and modeled the effects and uncertainties of major land‐use acts on protecting AGC stocks. Roughly 70% of the AGC stock in Brazil is estimated to be under legal protection, and an additional 20% is expected to be protected after areas in the Amazon with currently undesignated land undergo a tenure regularization. About 30% of the AGC stock is on private land, of which roughly two‐thirds are protected. The Cerrado, Amazon, and Caatinga biomes hold about 40%, 30%, and 20% of the unprotected AGC, respectively. Effective conservation of protected and unprotected carbon will depend on successful implementation of the Forest Act, and regularization of land tenure in the Amazon. Policy development that prioritizes unprotected AGC stocks is warranted to promote conservation of native vegetation beyond the legal requirements. However, different biomes and land tenure structures may require different policy settings considering local and regional specifics. Finally, the fate of current AGC stocks relies upon effective implementation of command and control mechanisms, considering that unprotected AGC in native vegetation on private land only accounts for 6.5% of the total AGC stock.  相似文献   

19.
A key challenge for humanity is how a future global population of 9 billion can all be fed healthily and sustainably. Here, we review how competition for land is influenced by other drivers and pressures, examine land-use change over the past 20 years and consider future changes over the next 40 years.Competition for land, in itself, is not a driver affecting food and farming in the future, but is an emergent property of other drivers and pressures. Modelling studies suggest that future policy decisions in the agriculture, forestry, energy and conservation sectors could have profound effects, with different demands for land to supply multiple ecosystem services usually intensifying competition for land in the future.In addition to policies addressing agriculture and food production, further policies addressing the primary drivers of competition for land (population growth, dietary preference, protected areas, forest policy) could have significant impacts in reducing competition for land. Technologies for increasing per-area productivity of agricultural land will also be necessary. Key uncertainties in our projections of competition for land in the future relate predominantly to uncertainties in the drivers and pressures within the scenarios, in the models and data used in the projections and in the policy interventions assumed to affect the drivers and pressures in the future.  相似文献   

20.
Land-use change is a major driver of the global biodiversity crisis, mainly via the fragmentation and loss of natural habitat. Although land-use changes will accelerate to meet humankind's growing demand for agricultural products, conservation planning rarely considers future land uses and how they may affect the connectivity of ecological networks. Here, we integrate land-use models with landscape fragmentation and connectivity analyses, to assess the effects of past and future land-use changes on the connectivity of protected area networks for a highly dynamic region in southeast Spain. Our results show a continued geographical polarisation of land use, with agricultural intensification and urban development in the coastal areas, and the abandonment of traditional land use in the mountains (e.g., 1100 km2 of natural vegetation are projected to be lost in coastal areas whereas 32 km2 of natural vegetation would recover in interior areas from 1991 to 2015). As a result, coastal protected areas will experience increasing isolation. The connectivity analyses reveal that the two protected area networks in place in the study area, the European “Natura 2000” and the Andalusian “RENPA” networks, include many landscape connectors. However, we identify two areas that currently lack protection but contain several important patches for maintaining the region's habitat connectivity: the northwestern and the southwestern slopes of the Sierra Cabrera and Bédar protected area. Our results highlight the importance of considering future land-use trajectories in conservation planning to maintain connectivity at the regional scale, and to improve the resilience of conservation networks.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号