Local faces,global flows: The role of land use and land cover in global environmental change

The emergence of land-use and land-cover change (LUCC) as one of the major themes within the global environmental change research community poses a series of difficult but not insurmountable problems. LUCC takes place incrementally through the operation of sets of human and biophysical forces largely specific to the locale in question, but cumulatively LUCC contributes significantly to global environmental change. Linking LUCC to global change requires the cooperation of the natural and social sciences to bridge the local to global dynamics involved. The International Geosphere-Biosphere Programme and the Human Dimensions of Global Environmental Change Programme are undertaking the development of an international research project with such aims in mind. This project seeks to improve understanding of LUCC dynamics by balancing the need for a nuanced understanding at the local level with the need from improved regional and global LUCC models. The rudiments of this effort and some of problems confronting it are outlined here.     

Living with the past: Uses of history for understanding landscape change and degradation

The analysis of land degradation is almost always ahistorical, and as a consequence is of diminished value. Global change, as it has come to be known, is thought of as a climatic phenomenon of this and the next century, but has actually been happening as a consequence of land use and climate variation for centuries. Land and water degradation are probably the most obvious manifestations of this global change. The various uses of historical analyses are exemplified in this paper to show their value as contextual explanations, possible analogues of future conditions, a library of experiments already performed, and a narrative of change.     

Appropriate experimental ecosystem warming methods by ecosystem, objective, and practicality

The temperature of the Earth is rising, and is highly likely to continue to do so for the foreseeable future. The study of the effects of sustained heating on the ecosystems of the world is necessary so that we might predict and respond to coming changes on both large and small spatial scales. To this end, ecosystem warming studies have been performed for more than 20 years using a variety of methods. These warming methods fall into two general categories: active and passive. Active warming methods include heat-resistance cables, infrared (IR) lamps and active field chambers. Passive warming methods include nighttime warming and passive field chambers. An extensive literature review was performed and all ecosystem warming study sites were compiled into a master list. These studies were divided by latitude and precipitation, as well as the method type used and response variables investigated. The goals of this study were to identify: (1) the most generally applicable, inexpensive and effective heating methods; and (2) areas of the world that are understudied or have been studied using only limited warming methods. It was found that the most generally applicable method, and the one that is most true to climate change predictions, is IR heating lamp installation. The least expensive method is passive chambers. The extreme lower and upper latitudes have been investigated least with ecosystem warming methods, and for the upper-mid-latitudes (60–80°) there have been limited studies published using methods other than passive chambers. Ecosystem warming method limitations and recommendations are discussed.     

河西地区土地利用/覆盖变化研究

土地利用/覆盖变化作为国际上全球变化研究的前沿与热点课题,是所有可持续发展相关问题的核心。河西地区为环境演化的敏感区和生态脆弱带,土地的演化过程和机制有其不同于东部地区的特殊规律。本文简要介绍了河西地区土地利用/覆盖变化过程,分析了土地利用/覆盖变化的动力机制,并就土地利用/覆盖变化对该地区自然环境与社会经济的影响进行了初步探讨,从而探索有利于该地区土地可持续发展的土地利用方式与土地覆盖类型。     

全球升温1.5℃和2.0℃情景下贵州省极端降水的变化特征

利用CCSM4和IPSL-CM5A-MR模式1961-2005年历史模拟和2006−2098年RCP2.6和RCP4.5排放情景下的逐日降水以及1961−2005年贵州省84个气象台站逐日降水资料,使用偏差校正改善模式模拟能力,通过降水强度、日最大降水量和强降水量等9个指标探究全球升温1.5℃和2.0℃条件下贵州省极端降水变化特征。结果表明：贵州省RCP2.6和RCP4.5情景下各极端降水指数虽然波动幅度较大,但总体上均呈现增加的趋势,且相对于基准期（1986−2005年）而言全球升温2.0℃时各极端降水指数增幅约为升温1.5℃时的两倍。在升温2.0℃下9个极端降水指数概率密度曲线尾端均向右延伸,表明在升温2.0℃情景下各极端降水指数中高值出现的概率增大。因此,将全球升温控制在1.5℃而不是2.0℃意义重大。     

Greenhouse gas flux from cropland and restored wetlands in the Prairie Pothole Region

It has been well documented that restored wetlands in the Prairie Pothole Region of North America do store carbon. However, the net benefit of carbon sequestration in wetlands in terms of a reduction in global warming forcing has often been questioned because of potentially greater emissions of greenhouse gases (GHGs) such as nitrous oxide (N₂O) and methane (CH₄). We compared gas emissions (N₂O, CH₄, carbon dioxide [CO₂]) and soil moisture and temperature from eight cropland and eight restored grassland wetlands in the Prairie Pothole Region from May to October, 2003, to better understand the atmospheric carbon mitigation potential of restored wetlands. Results show that carbon dioxide contributed the most (90%) to net-GHG flux, followed by CH₄ (9%) and N₂O (1%). Fluxes of N₂O, CH₄, CO₂, and their combined global warming potential (CO₂ equivalents) did not significantly differ between cropland and grassland wetlands. The seasonal pattern in flux was similar in cropland and grassland wetlands with peak emissions of N₂O and CH₄ occurring when soil water-filled pore space (WFPS) was 40-60% and >60%, respectively; negative CH₄ fluxes were observed when WFPS approached 40%. Negative CH₄ fluxes from grassland wetlands occurred earlier in the season and were more pronounced than those from cropland sites because WFPS declined more rapidly in grassland wetlands; this decline was likely due to higher infiltration and evapotranspiration rates associated with grasslands. Our results suggest that restoring cropland wetlands does not result in greater emissions of N₂O and CH₄, and therefore would not offset potential soil carbon sequestration. These findings, however, are limited to a small sample of seasonal wetlands with relatively short hydroperiods. A more comprehensive assessment of the GHG mitigation potential of restored wetlands should include a diversity of wetland types and land-use practices and consider the impact of variable climatic cycles that affect wetland hydrology.     

Predicted trends of soil erosion and sediment yield from future land use and climate change scenarios in the Lancang–Mekong River by using the modified RUSLE model

Soil erosion and sediments in the Lancang-Mekong River Basin as a result of climate change and changes in land use pose a threat to the existence of the riparian people, biodiversity and ecosystems. This study seeks to assess the annual soil erosion in terms of spatial distribution and the trends of sediment yield with the climate and land changes in future scenarios in 2030 and 2040 through the modified RUSLE model. Future lands were simulated by using the MLP artificial neural network and the Markov chain analysis. The future climate was examined by using the Max Planck Institute model, which showed a corrected bias and downscaled grid size under the Representative Concentration Pathways (RCPs). The simulated land use indicated that the forest areas were converted mostly to agricultural lands and urban areas. In the future, the average rainfall under all RCP scenarios is higher than that from the historical period. The R and C factors changed constantly, thereby affecting the soil erosion rate and sediment yield. The maximum erosion was estimated at approximately 21,000 and 21,725 t/km²/y under RCP8.5 in both years. Meanwhile, the results of sediment yield in 2030 and 2040 under RCP scenarios were much higher when compared to historical sediment data around 66.3% and 71.2%, respectively. Thailand's plateau, some parts of Cambodia and Laos PDR and the Mekong Delta are vulnerable to increase soil erosion and sediment yield. Measures to address these issues need to be planned to prepare and mitigate the possible effects, especially the loss of storage capacity in dams.     

The impact of climate change on cherry trees and other species in Japan

Studies from throughout the world have provided evidence that climate change is already affecting the ecology and persistence of species. Japan contributes valuable insights into understanding these changes through long-term records of the timing of cherry blossoms and other phenomena of ecological and cultural interest. The wide latitudinal spread of Japan also provides an opportunity to examine species over a broad range of environmental conditions. In this review, we examine phenological studies that have taken place in Japan and summarize their significance to climate change and conservation research. In Kyoto, records of the timing of celebrations of cherry blossom festivals going back to the 9th century reconstruct the past climate and demonstrate the local increase in temperature associated with global warming and urbanization. This record is probably the longest annual record of phenology from anyplace in the world and shows that cherries are currently flowering earlier than they have at any time during the previous 1200 years. Detailed mapping of cherry tree flowering times in and around Osaka and other cities in Japan show that urbanization causes plants to flower earlier within the city environs than in nearby parks and outlying suburban areas. Flowering records from a large cherry arboretum at Mt. Takao, on the outskirts of Tokyo, show that both among and within species, early flowering is associated with greater responsiveness to temperature variation. Lastly, records of phenology for a wide range of plants and animals recorded at over 100 weather stations throughout Japan show that species vary greatly in their phenological responses to climate change, and highlight ecological relationships that need to be investigated in the field. Together, these studies provide important insights into how species are responding to climate change in Japan. Further research, particularly targeted field observations and experiments, is needed to build on these findings and to improve our understanding of how climate change is altering biological communities and how it will continue to affect them in the future.     

Comment on the comment by Amthor et al. on “Appropriate experimental ecosystem warming methods” by Aronson and McNulty

In a recent comment on the paper by Aronson and McNulty (2009) about “Appropriate experimental ecosystem warming methods by ecosystem, objective, and practicality”, Amthor et al. (2010) state that infrared lamps do not warm open-field plots by the mechanism expected with global warming. While this statement is correct, in the aftermath of their comment, confusion exists about how warming with infrared heaters can be related to global warming. This comment illustrates how infrared heating at “constant temperature rise” relates in a quantitative way to anticipated global warming. Amthor et al. (2010) also state that changes in vapor pressure gradient from leaf to atmosphere are an issue with infrared heating, but this problem can be minimized with supplemental irrigations in controlled amounts. Therefore, “constant temperature rise” infrared warming experiments with supplemental irrigations are a viable T-FACE (temperature free-air controlled enhancement) that can be used in combination with CO₂-FACE to produce conditions more representative of future open-fields than can be done with chambers with their many known artifacts.     

Distinct and combined impacts of climate and land use scenarios on water availability and sediment loads for a water supply reservoir in northern Morocco

The objective of this study was to examine the impacts of climate and land use changes on water availability and sediment loads for a water supply reservoir in northern Morocco using data-intensive simulation models in a data-scarce region. Impacts were assessed by comparing the simulated water and sediment entering the reservoir between the future period 2031–2050 and the 1983–2010 reference period. Three scenarios of land use change and two scenarios of climate change were developed in the Tleta watershed. Simulations under current and future conditions were performed using the Soil and Water Assessment Tool (SWAT) model. The simulations showed that climate change will lead to a significant decrease in the annual water supply to the reservoir (−16.9% and −27.5%) and in the annual volume of sediment entering the reservoir (−7.4% and −12.6%), depending on the climate change scenarios tested. The three scenarios of land use change will lead to a moderate change in annual water inflow into the reservoir (between −6.7% and +6.2%), while causing a significant decrease in sediment entering the reservoir (−37% to −24%). The combined impacts of climate and land use changes will cause a reduction in annual water availability (−9.9% to −33.3%) and sediment supplies (−28.7% to −45.8%). As a result, the lifetime of the reservoir will be extended, but at the same time, the risk of water shortages will increase, especially from July to March. Therefore, alternative water resources must be considered.     

Human and climatic drivers of land and water use from 1997 to 2019 in Tarim River basin,China

Climate and human activities change spatial and temporal distribution of water and land use. The Tarim River, the largest inland river in China, faced a long-term exploitation of land and water over a rapid economic development. We analyzed land and water use from 1997 to 2019 in Tarim River Basin by Landsat images, and data on hydrology, climate, population, economy and PM_2.5 (air particulate matter ≤2.5 μm). Agricultural land expanded the fastest (4–11%), followed by natural vegetation (15–16%) and water area (4–5%) with population and economic increase. Air quality (PM_2.5 μg m⁻³) improved in upper (62–27) and middle (48–17) reaches. The water area in lower increase 5% because of ecological water delivery since 2000. Land use in the lower reach was dominated by agriculture, where the downstream runoff consumption increased by 6.8 times. The average annual air temperature and precipitation gradually increased by 0.5 °C and 51 mm in source and 0.9 °C and 30 mm in main reaches. The average annual water consumption in upper and middle reaches was 4 × 10⁹ m³, accounting for 87% of input runoff in the main reach. Water consumption in middle reach increased by 33 times in 2009–2017. The industry structure was changing from primary to secondary and tertiary industry. To sum up, implementation of water saving strategies and ecological water delivery restored local ecology. Sustainable strategies should be applied facing industrialization. Furthermore, changing the industry structure and restoring the degraded farmlands to grasslands or forests would keep sustainability of Tarim River Basin.     

Regional differences in patterns of fish species loss with changing land use

Human-centered land use causes ecosystem degradation and loss of biodiversity in streams, yet such processes may be highly heterogeneous among species and regions. We quantified fish species sensitivity to several classes of land use and determined if trends varied among three geoclimatic regions of Maryland, USA. Our approach compares the cumulative frequency distribution (CFD) of sites where a species was expected to occur to the CFD of those where it was collected to estimate the species-specific maximum degree of land use tolerated and the minimal amount that may induce an impact. Fishes were most vulnerable to urban land use gradients, though trends were region-specific with heightened sensitivity in the Piedmont (64-72% of species negatively affected) relative to the Coastal Plain (45-52% negatively affected). Species found in both regions exhibited greater vulnerability to urbanization in the Piedmont. Responses to agricultural land use were less severe though trends were region-specific as well with the least sensitive in the Piedmont and the greatest negative impact in the Highlands region. In many cases, reduced population abundances were detected at lower levels of land use relative to the range where the species was apparently extirpated. Our results demonstrate that population reduction and species loss due to land use change differs substantially among regions, even within a single species. Greater sensitivity observed in abundance-weighted analyses implies that further loss of fish diversity may be impending in impacted streams. Our results have direct application to prioritize conservation resources and forecast future declines in species distributions and biodiversity.     

Future productivity of fallow systems in Sub-Saharan Africa: Is the effect of demographic pressure and fallow reduction more significant than climate change?

In this century climate change is assumed to be the major driver for changes in agricultural systems and crop productivity at the global scale. However, due to spatial differences in cropping systems and in the magnitude of climatic change regional variations of climate change impact are expected. Furthermore, the recent climate projections are highly uncertain for large parts of West Africa. In particular with respect to annual precipitation and variability the projections vary between trends with decreasing precipitation and trends with slightly increasing precipitation within the next decades. On the other hand, the extensive fallow systems in this region suffer from increasing population pressure, which compromises soil fertility restoration. In the Republic of Benin, the demographic projections for the first half of this century indicate a continuous growth of the population with a narrow interval of confidence. Thus, in the absence of an adequate soil fertility management with judicious use of mineral fertilizers, the soil degradation process with decreasing crop yields is expected to continue. The objective of this paper was, therefore, to quantify the regional effect of future population growth on crop yields in West Africa and to compare it with the potential effects of climate change scenarios. Three land use scenarios (L1, L2 and L3) for the Upper Ouémé catchment where derived from different demographic projections combined with assumptions regarding future road networks and legal frameworks for forest protection using the CLUE-S modeling approach. The fallow-cropland ratio decreased in the three scenarios from 0.87 in the year 2000 to 0.66, 0.48 and 0.68 for L1, L2 and L3, respectively in 2050. Based on the projected ratio of fallow and cropland, trends of maize yield for the three land use scenarios were calculated using the EPIC (Environmental Policy Integrated Climate) model coupled with a spatial database. Maize yields followed the decreasing trend of the fallow-cropland ratio and estimated yield reductions amounted to up to 24% in the period 2021-2050. This trend was compared with the impact of the SRES climate scenarios A1B and B1 based on the output of the GCM ECHAM5 downscaled with the REMO model and the A1B scenario output of the GCM HADC3Q0 downscaled with the RCMs SMHIRCA and HADRM3P. The yield reductions due to the projected climate change in the three models accounted for a yield decrease of up to 18% (REMO A1B scenario) in the same period. Taking into account the smaller uncertainties in the scenario assumptions and in the model output of the land use scenarios, it is concluded that, in low input fallow systems in West Africa, land use effects will be at least as important as climate effects within the next decades.     

Projected large-scale range reductions of northern-boreal land bird species due to climate change

Climate change is projected to be particularly strong in the northern latitudes. Thus, boreal or arctic species are especially susceptible to the effects of climate warming. In this work we forecasted changes in the distributions of 27 northern land bird species in the 21st century, based on predicted rates of climate change. We used climate and bird atlas data of Finland and northern Norway from 1971-1990 to establish bioclimatic envelope models for each species. Next, these models were applied to two climate scenarios (A2 and B1) from the general circulation model HadCM3 to forecast potential future distributions of the study species over a larger area also covering parts of nearby Sweden and Russia. This area stretches through the boreal and continental arctic zone in northern Europe. In the A2 scenario the predicted global change in mean temperature is 3.8 °C by 2100 and in the B1 scenario 2.0 °C. Our results suggest that most of the northern land bird species will lose most of their climatic space by 2080 both in the more severe (A2, average predicted range decline: -83.6%) and in the less severe scenario (B1, average change: -73.6%). A large proportion (over two thirds) of the species considered here is thus susceptible to major range contractions in this geographical region. These climate change-induced threats are of importance because the Arctic Ocean represents a natural barrier for northward movement of species. To reduce the negative effects of climate change on the northern species, relatively large areas of continuous habitats in a connected reserve network should be preserved.     

Conservation planning under climate change: Toward accounting for uncertainty in predicted species distributions to increase confidence in conservation investments in space and time

Climate warming challenges our approach to building systems of protected areas because it is likely to drive accelerating shifts in species distributions, and the projections of those future species distributions are uncertain. There are several important sources of uncertainty intrinsic to using species occurrence projections for reserve system design including uncertainty in the number of occurrences captured by any reserve selection solution, and uncertainty arising from the different approaches used to fit predictive models. Here we used the present and future predicted distributions of Iberian herptiles to analyze how dynamics and uncertainty in species distributions may affect decisions about resource allocation for conservation in space and time. We identified priority areas maximizing coverage of current and future (2020 and 2080) predicted distributions of 65 species, under “Mild” and “Severe” uncertainty. Next, we applied a return-on-investment analysis to quantify and make explicit trade-offs between investing in areas selected when optimizing for different times and with different uncertainty levels. Areas identified as important for conservation in every time frame and uncertainty level were the ones considered to be robust climate adaptation investments, and included chiefly already protected areas. Areas identified only under “Mild” uncertainty were considered good candidates for investment if extra resources are available and were mainly located in northern Iberia. However, areas selected only in the “Severe” uncertainty case should not be completely disregarded as they may become climatic refugia for some species. Our study provides an objective methodology to deliver “no regrets” conservation investments.     

Arctic sea ice trends and narwhal vulnerability

Conservation measures related to global climate change require that species vulnerability be incorporated into population risk models, especially for those that are highly susceptible to rapid or extreme changes due to specialized adaptation. In the case of Arctic cetaceans, effects of climate change on habitat and prey availability have been subject to intense speculation. Climate perturbations may have significant impacts on the fitness and success of this group, yet measuring these parameters for conservation purposes is complicated by remote and offshore preferences. The narwhal (Monodon monoceros) in Baffin Bay occupies a habitat where reversed (increasing) regional sea ice trends have been detected over 50 years. We used a combination of long-term narwhal satellite tracking data and remotely sensed sea ice concentrations to detect localized habitat trends and examine potential vulnerability. Spatial and temporal variability in the fraction of open water were examined on two narwhal wintering grounds between November and April, 1978-2001 using approximate sea ice concentrations derived from microwave SSMR/SSMI passive brightness temperatures. Less than 3% open water was available to narwhals between 15 January and 15 April, and reached minima of 0.5% open water at the end of March (125 km² out of a 25,000 km² area). Decreasing trends in the fraction of open water, together with increasing trends in interannual variability, were detected on both wintering grounds, significantly in northern Baffin Bay (−0.04% per year, SE 0.02). The limited number of leads and cracks available to narwhals during the winter, in combination with localized decreasing trends in open water and high site fidelity, suggests vulnerability to changes in Arctic sea ice conditions. Increasing risk of ice entrapments, many of which may go undetected in remote offshore areas, should be incorporated into population risk assessments as this may exceed the natural response capacity of the species.     

El Niño induced local extinction of coral reef bryozoan species from Northern Bahia, Brazil

The 1997-1998 El-Niño Southern Oscillation was the most severe on record and dramatically impacted corals worldwide. However, the effect of this event on the associated community of reef organisms has received much less attention. The composition of the bryozoan assemblage from the coral reefs of Northern Bahia, Brazil were monitored annually from 1995 to 2000, allowing the investigation of the effects of this large-scale stressor on an important, diverse, yet understudied component of the coral reef system. Bryozoan samples (35 replicates/reef) were collected during April/May from four shallow bank reefs (10-40 m depth) located a few kilometres off the coast, together with measurements of the associated environmental parameters. Currently 157 species have been recorded from the study area, but significant reductions in density and diversity were apparent between pre- and post El-Niño Southern Oscillation (ENSO) years, multivariate analysis denoting significant changes in assemblage composition. A total of 61 species were unrecorded following the 1997-1998 ENSO event (22 species from 1997; 25 further species from 1998 and 14 more from 1999). These included several species endemic to Brazil, suggesting that the 1997-1998 ENSO has had a marked influence on the reef bryozoan community, resulting in the local extinction of several species. Bryozoan mortalities were probably initiated by elevated temperatures, but continued disappearance of species for 2 years after ENSO suggests other indirect factors are also influential. These results demonstrate that ENSO events can have severe long-term impacts on the biodiversity of coral reefs, with important conservation consequences.     

Incorporating anthropogenic threats into evaluations of regional biodiversity and prioritisation of conservation areas in the Limpopo Province, South Africa

Recent attempts to streamline the identification of areas requiring immediate conservation attention have resulted in the development of prioritisation procedures that identify areas of biodiversity importance facing large threats in the near future. This study incorporated biodiversity data on bird and vegetation distribution with an assessment of land use suitability for cultivation and afforestation for the Limpopo Province of South Africa. The low altitude savanna regions in the northeast contain high species diversity, but are unsuitable to alternative forms of land use and are well conserved (by e.g., the Kruger National Park). The central and eastern mountain ranges, sites of high biodiversity, are suitable to dryland cultivation and afforestation and are thus potential conservation priorities. Areas with high biodiversity values, e.g., irreplaceable areas that contain biodiversity features essential for meeting conservation targets, were then investigated for their potential land-use threats in order to prioritise those needing immediate conservation actions. We suggest how losses of biodiversity could be minimised by reaching such decisions more quickly.     

Landscape history and soil properties affect grassland decline and plant species richness in rural landscapes

Past semi-natural grassland extent is thought to have a major influence on contemporary species richness in rural landscapes. The loss of grasslands over the last 300 years was reconstructed for 12 rural landscapes in Sweden, ranging from open modern agricultural landscapes to more forested landscapes. Old maps and aerial photographs from 1950s and today were used to reconstruct landscape patterns in four time-steps to investigate how present plant species richness relates to past grassland extent and decline in old and new grassland habitats. The relative importance of soil properties on the timing of grassland decline was assessed. Plant species occurrence was recorded in managed and abandoned grassland habitats in each landscape.Past and present grassland distribution was a major factor in determining plant species patterns found in grasslands today. All landscapes had an average of 80% grassland 300 years ago. Since then grassland has declined by 90% across all landscapes. Proportion of clay soils influenced the timing of grassland decline, where grasslands in landscapes dominated by clay soils were conversed to crop-fields more than 100 years ago. Grasslands on coarser soils declined later, primarily to forest. Landscapes with more than 10% semi-natural grassland left today had 50% higher species richness in all grasslands, including both abandoned and new grassland. Time since major grassland decline also seems to have an effect on the landscapes’ species richness. The results show that plant species patterns in grasslands at local scales are determined by broader landscape processes which may have occurred many centuries ago.