Climate-driven Vegetation Research Articles

Microbial Evolution Drives Adaptation of Substrate Degradation on Decadal to Centennial Time Scales Relevant to Global Change.

Understanding microbial adaptation is crucial for predicting how soil carbon dynamics and global biogeochemical cycles will respond to climate change. This study employs the DEMENT model of microbial decomposition, along with empirical mutation and dispersal rates, to explore the roles of mutation and dispersal in the adaptation of soil microbial populations to shifts in litter chemistry, changes that are anticipated with climate-driven vegetation dynamics. Following a change in litter chemistry, mutation generally allows for a higher rate of litter decomposition than dispersal, especially when dispersal predominantly introduces genotypes already present in the population. These findings challenge the common idea that mutation rates are too low to affect ecosystem processes on ecological timescales. These results demonstrate that evolutionary processes, such as mutation, can help maintain ecosystem functioning as the climate changes.

Pursuit and escape drive fine-scale movement variation during migration in a temperate alpine ungulate

Climate change reduces snowpack, advances snowmelt phenology, drives summer warming, alters growing season precipitation regimes, and consequently modifies vegetation phenology in mountain systems. Elevational migrants track spatial variation in seasonal plant growth by moving between ranges at different elevations during spring, so climate-driven vegetation change may disrupt historic benefits of migration. Elevational migrants can furthermore cope with short-term environmental variability by undertaking brief vertical movements to refugia when sudden adverse conditions arise. We uncover drivers of fine-scale vertical movement variation during upland migration in an endangered alpine specialist, Sierra Nevada bighorn sheep (Ovis canadensis sierrae) using a 20-year study of GPS collar data collected from 311 unique individuals. We used integrated step-selection analysis to determine factors that promote vertical movements and drive selection of destinations following vertical movements. Our results reveal that relatively high temperatures consistently drive uphill movements, while precipitation likely drives downhill movements. Furthermore, bighorn select destinations at their peak annual biomass and maximal time since snowmelt. These results indicate that although Sierra Nevada bighorn sheep seek out foraging opportunities related to landscape phenology, they compensate for short-term environmental stressors by undertaking brief up- and downslope vertical movements. Migrants may therefore be impacted by future warming and increased storm frequency or intensity, with shifts in annual migration timing, and fine-scale vertical movement responses to environmental variability.

Pollution and Climatic Influence on Trees in the Siberian Arctic Wetlands

Siberian Arctic wetlands located within the planetary “warming hotspot” experience pronounced climate-driven vegetation cover changes. Together with warming, wetlands, which are located within the influence of Norilsk copper and nickel industry (69.35° N, 88.12° E), have been strongly influenced by industrial pollutions (sulfur dioxide mostly) since the 1940s. In addition, petroleum products release occurred in 2020 that potentially influenced vegetation vigor. We studied the combined effect of climate warming and pollution on the larch (Larix sibirica Ledeb.) and shrubs’ (Salix spp. and alder, Duschekia fruticosa) growth. Using satellite data (MODIS and Sentinel) processing, we mapped wetlands within the study area. We used on-ground survey, and applied dendrochronology, climate variables, and emissions rate analysis. We sampled woods (kerns) and, based on the tree ring analysis, generated trees and shrubs growth index (GI) chronologies. We analyzed the influence of the SO2 emissions and eco-climate variables (air temperatures, precipitation, soil moisture, and drought index SPEI) on the larch and shrubs GI. We mapped GPP and NPP (gross and net primary productivity) and vegetation index NDVI and temporal trends of these indexes based on the MODIS-derived products. We found that chronic SO2 influence led to larch trees GI decrease that was followed by tree mortality, which was observed until the end of 1990. Since the beginning of the 2000s, the GI of larch and shrubs has increased, which is correlated with elevated air and soil temperature and growth season prolongation, whereas excessive soil moisture negatively influenced GI. Together with that, increasing trends of vegetation indexes (GPP, NPP, and NDVI) were observed on the part of wetland within the zone of former trees’ heavy damage and mortality. The trends began mostly in 2003–2005 and were caused by emissions volume decrease and warming, together with resistant species’ (willows, graminoids, bushes, and birch) growth and invasion. We suggested that increasing productivity trends might partly be attributed to nitrogen fertilization caused by NOx emissions. Finally, we found that diesel fuel spill which happened in 2020 caused no influence on the larch, whereas some aquatic species (mosses mostly) were damaged.

Combined impacts of future climate-driven vegetation changes and socioeconomic pressures on protected areas in Africa.

Africa's protected areas (PAs) are the last stronghold of the continent's unique biodiversity, but they appear increasingly threatened by climate change, substantial human population growth, and land-use change. Conservation planning is challenged by uncertainty about how strongly and where these drivers will interact over the next few decades. We investigated the combined future impacts of climate-driven vegetation changes inside African PAs and human population densities and land use in their surroundings for 2 scenarios until the end of the 21st century. We used the following 2 combinations of the shared socioeconomic pathways (SSPs) and representative greenhouse gas concentration pathways (RCPs): the "middle-of-the-road" scenario SSP2-RCP4.5 and the resource-intensive "fossil-fueled development" scenario SSP5-RCP8.5. Climate change impacts on tree cover and biome type (i.e., desert, grassland, savanna, and forest) were simulated with the adaptive dynamic global vegetation model (aDGVM). Under both scenarios, most PAs were adversely affected by at least 1 of the drivers, but the co-occurrence of drivers was largely region and scenario specific. The aDGVM projections suggest considerable climate-driven tree cover increases in PAs in today's grasslands and savannas. For PAs in West Africa, the analyses revealed climate-driven vegetation changes combined with hotspots of high future population and land-use pressure. Except for many PAs in North Africa, future decreases in population and land-use pressures were rare. At the continental scale, SSP5-RCP8.5 led to higher climate-driven changes in tree cover and higher land-use pressure, whereas SSP2-RCP4.5 was characterized by higher future population pressure. Both SSP-RCP scenarios implied increasing challenges for conserving Africa's biodiversity in PAs. Our findings underline the importance of developing and implementing region-specific conservation responses. Strong mitigation of future climate change and equitable development scenarios would reduce ecosystem impacts and sustain the effectiveness of conservation in Africa.

Time-series maps reveal widespread change in plant functional type cover across Arctic and boreal Alaska and Yukon

Widespread changes in the distribution and abundance of plant functional types (PFTs) are occurring in Arctic and boreal ecosystems due to the intensification of disturbances, such as fire, and climate-driven vegetation dynamics, such as tundra shrub expansion. To understand how these changes affect boreal and tundra ecosystems, we need to first quantify change for multiple PFTs across recent years. While landscape patches are generally composed of a mixture of PFTs, most previous moderate resolution (30 m) remote sensing analyses have mapped vegetation distribution and change within land cover categories that are based on the dominant PFT; or else the continuous distribution of one or a few PFTs, but for a single point in time. Here we map a 35 year time-series (1985–2020) of top cover (TC) for seven PFTs across a 1.77 × 106 km2 study area in northern and central Alaska and northwestern Canada. We improve on previous methods of detecting vegetation change by modeling TC, a continuous measure of plant abundance. The PFTs collectively include all vascular plants within the study area as well as light macrolichens, a nonvascular class of high importance to caribou management. We identified net increases in deciduous shrubs (66 × 103 km2), evergreen shrubs (20 × 103 km2), broadleaf trees (17 × 103 km2), and conifer trees (16 × 103 km2), and net decreases in graminoids (−40 × 103 km2) and light macrolichens (−13 × 103 km2) over the full map area, with similar patterns across Arctic, oroarctic, and boreal bioclimatic zones. Model performance was assessed using spatially blocked, nested five-fold cross-validation with overall root mean square errors ranging from 8.3% to 19.0%. Most net change occurred as succession or plant expansion within areas undisturbed by recent fire, though PFT TC change also clearly resulted from fire disturbance. These maps have important applications for assessment of surface energy budgets, permafrost changes, nutrient cycling, and wildlife management and movement analysis.

Human practices behind the aquatic and terrestrial ecological decoupling to climate change in the tropical Andes

Anthropogenic climate change and landscape alteration are two of the most important threats to the terrestrial and aquatic ecosystems of the tropical Americas, thus jeopardizing water and soil resources for millions of people in the Andean nations. Understanding how aquatic ecosystems will respond to anthropogenic stressors and accelerated warming requires shifting from short-term and static to long-term, dynamic characterizations of human-terrestrial-aquatic relationships. Here we use sediment records from Lake Llaviucu, a tropical mountain Andean lake long accessed by Indigenous and post-European societies, and hypothesize that under natural historical conditions (i.e., low human pressure) vegetation and aquatic ecosystems' responses to change are coupled through indirect climate influences—that is, past climate-driven vegetation changes dictated limnological trajectories. We used a multi-proxy paleoecological approach including drivers of terrestrial vegetation change (pollen), soil erosion (Titanium), human activity (agropastoralism indicators), and aquatic responses (diatoms) to estimate assemblage-wide rates of change and model their synchronous and asynchronous (lagged) relationships using Generalized Additive Models. Assemblage-wide rate of change results showed that between ca. 3000 and 400 calibrated years before present (cal years BP) terrestrial vegetation, agropastoralism and diatoms fluctuated along their mean regimes of rate of change without consistent periods of synchronous rapid change. In contrast, positive lagged relationships (i.e., asynchrony) between climate-driven terrestrial pollen changes and diatom responses (i.e., asynchrony) were in operation until ca. 750 cal years BP. Thereafter, positive lagged relationships between agropastoralism and diatom rates of changes dictated the lake trajectory, reflecting the primary control of human practices over the aquatic ecosystem prior European occupation. We interpret that shifts in Indigenous practices (e.g., valley terracing) curtailed nutrient inputs into the lake decoupling the links between climate-driven vegetation changes and the aquatic community. Our results demonstrate how rates of change of anthropogenic and climatic influences can guide dynamic ecological baselines for managing water ecosystem services in the Andes.

Deep learning projects future warming-induced vegetation growth changes under SSP scenarios

Climate warming has been projected to enhance vegetation growth more strongly in higher latitudes than in lower latitudes, but different projections show distinct regional differences. By employing big data analysis (deep learning), we established gridded, global-scale, climate-driven vegetation growth models to project future changes in vegetation growth under SSP scenarios. We projected no substantial trends of vegetation growth change under the sustainable development scenario (SSP1-1.9) by the end of the 21st century. However, the increase of vegetation growth driven by climate warming shows distinct regional variability under the scenario representing high carbon emissions and severe warming (SSP5-8.5), especially in Northeast Asia where growth could increase by (6.00% ± 4.21%). This may be attributed to the high temperature sensitivities of the deciduous needleleaf forests and permanent wetlands in these regions. When the temperature sensitivity that is defined as permutation importance in deep learning is greater than 0.05, the increase in vegetation growth will be more prominent. In addition, an extreme temperature increase across grasslands, as well as changing land-use management in northern China may also influence the vegetation growth in the future. The results suggest that the sustainable development scenario can maintain stable vegetation growth, and it may be a reliable way to mitigate global warming due to potential climate feedbacks driven by vegetation changes in boreal regions. Deciduous needleleaf forests will be a centre of greening in the future, and it should become the focus of future vegetation dynamics modelling studies and projections.

Late Pleistocene shrub expansion preceded megafauna turnover and extinctions in eastern Beringia

The collapse of the steppe-tundra biome (mammoth steppe) at the end of the Pleistocene is used as an important example of top-down ecosystem cascades, where human hunting of keystone species led to profound changes in vegetation across high latitudes in the Northern Hemisphere. Alternatively, it is argued that this biome transformation occurred through a bottom-up process, where climate-driven expansion of shrub tundra (Betula, Salix spp.) replaced the steppe-tundra vegetation that grazing megafauna taxa relied on. In eastern Beringia, these differing hypotheses remain largely untested, in part because the precise timing and spatial pattern of Late Pleistocene shrub expansion remains poorly resolved. This uncertainty is caused by chronological ambiguity in many lake sediment records, which typically rely on radiocarbon (14C) dates from bulk sediment or aquatic macrofossils-materials that are known to overestimate the age of sediment layers. Here, we reexamine Late Pleistocene pollen records for which 14C dating of terrestrial macrofossils is available and augment these data with 14C dates from arctic ground-squirrel middens and plant macrofossils. Comparing these paleovegetation data with a database of published 14C dates from megafauna remains, we find the postglacial expansion of shrub tundra preceded the regional extinctions of horse (Equus spp.) and mammoth (Mammuthus primigenius) and began during a period when the frequency of 14C dates indicates large grazers were abundant. These results are not consistent with a model of top-down ecosystem cascades and support the hypothesis that climate-driven habitat loss preceded and contributed to turnover in mammal communities.

Global acceleration in rates of vegetation change over the past 18,000 years.

Global vegetation over the past 18,000 years has been transformed first by the climate changes that accompanied the last deglaciation and again by increasing human pressures; however, the magnitude and patterns of rates of vegetation change are poorly understood globally. Using a compilation of 1181 fossil pollen sequences and newly developed statistical methods, we detect a worldwide acceleration in the rates of vegetation compositional change beginning between 4.6 and 2.9 thousand years ago that is globally unprecedented over the past 18,000 years in both magnitude and extent. Late Holocene rates of change equal or exceed the deglacial rates for all continents, which suggests that the scale of human effects on terrestrial ecosystems exceeds even the climate-driven transformations of the last deglaciation. The acceleration of biodiversity change demonstrated in ecological datasets from the past century began millennia ago.

The pace of Holocene vegetation change

Paleoecology Although much is known about the rapid environmental changes that have occurred since the Industrial Revolution, the patterns of change over the preceding millennia have been only patchily understood. Using a global set of >1100 fossil pollen records, Mottl et al. explored the rates of vegetation change over the past 18,000 years (see the Perspective by Overpeck and Breshears). The authors show that the rates of change accelerated markedly during the Late Holocene (∼4.6 to 2.9 thousand years ago), even more rapidly than the climate-driven vegetation changes associated with the end of the last glacial period. In addition, the Late Holocene acceleration began for terrestrial communities as a whole, suggesting that the acceleration in turnover over the past two centuries is the tip of a deeper trend. Science , abg1685, this issue p. [860][1]; see also abi9902, p. [786][2] [1]: /lookup/doi/10.1126/science.abg1685 [2]: /lookup/doi/10.1126/science.abi9902

Cascading response of flora and terrestrial mollusks to last deglacial warming

The cascading impacts of climate-driven vegetation change on terrestrial invertebrates via trophic and habitat routes is a matter of outstanding concern. However, the combined responses of plant-animal associations in terrestrial ecosystems have seldom been reported on geological timescales, which raises the important questions of how frequently and to what extent such multi-trophic shifts in taxa have occurred during previous warming scenarios. Here we use a combination of mollusk, palynological, and climatic proxy evidence preserved within loess deposits in the southern Chinese Loess Plateau (CLP) to demonstrate how long-term changes in hydroclimatic dynamics during the past 26 kyr were reflected in the subsequent ecological changes. Specifically, there was a shift from a predominantly cold-tolerant mollusk fauna in a dry-steppe environment under cold-dry conditions during the last glacial, to a predominantly thermal-mesophilous fauna in a meadow-steppe environment under a warm temperate climate in the early-middle Holocene. Warmth-adapted mollusk species such as Opeas striatissimum and Punctum orphana were found to have been associated with several deciduous tree taxa (e.g., Corylus, Quercus, and Pterocarya) in both the Holocene record and in the modern ecosystem (based on surveys of 356 surface-soil plots). This suggests there is a clear ecological interdependency between specific vegetation types and mollusk assemblages. As such, the long-term vegetation-mollusk fossil records highlight the indirect impacts of climate change on terrestrial invertebrate turnover via plant-derived food structure and habitat routes, with major implications for understanding how these ecosystems are likely to respond to future climate changes.

Asynchronous carbon sink saturation in African and Amazonian tropical forests.

Structurally intact tropical forests sequestered about half of the global terrestrial carbon uptake over the 1990s and early 2000s, removing about 15 per cent of anthropogenic carbon dioxide emissions1-3. Climate-driven vegetation models typically predict that this tropical forest 'carbon sink' will continue for decades4,5. Here we assess trends in the carbon sink using 244 structurally intact African tropical forests spanning 11 countries, compare them with 321 published plots from Amazonia and investigate the underlying drivers of the trends. The carbon sink in live aboveground biomass in intact African tropical forests has been stable for the three decades to 2015, at 0.66 tonnes of carbon per hectare per year (95 per cent confidence interval 0.53-0.79), in contrast to the long-term decline in Amazonian forests6. Therefore the carbon sink responses of Earth's two largest expanses of tropical forest have diverged. The difference is largely driven by carbon losses from tree mortality, with no detectable multi-decadal trend in Africa and a long-term increase in Amazonia. Both continents show increasing tree growth, consistent with the expected net effect of rising atmospheric carbon dioxide and air temperature7-9. Despite the past stability of the African carbon sink, our most intensively monitored plotssuggest a post-2010 increase in carbon losses, delayed compared to Amazonia, indicating asynchronous carbon sink saturation on the two continents. A statistical model including carbon dioxide, temperature, drought and forest dynamics accounts for the observed trends and indicates a long-term future decline in the African sink, whereas the Amazonian sink continues to weaken rapidly. Overall, the uptake of carbon into Earth's intact tropical forests peaked in the 1990s. Given that the global terrestrial carbon sink is increasing in size, independent observations indicating greater recent carbon uptake into the Northern Hemisphere landmass10 reinforce our conclusion that the intact tropical forest carbon sink has already peaked. This saturation and ongoing decline of the tropical forest carbon sink has consequences for policies intended to stabilize Earth's climate.

No treeline advance over the last 50 years in subarctic western and central Canada and the problem of vegetation misclassification in remotely sensed data

ABSTRACTIn this study we examined (1) whether there has been significant tree cover change over the period 1960–2010 in a 960,000 km2 subarctic study region in western and central Canada, and (2) the degree to which Global Forest Change (GFC) tree cover data agree with other datasets. We compared GFC tree cover to cover estimates from air photos (c. 1960), ground-level plot data (c. 1982–84), annotated low-level oblique photographs (c. 2005–09), and air photo footprints on the World Imagery Base Map (c. 2010). Tree cover changes since 1960 varied by physiographic and ecological regions. Afforestation was modest to non-significant depending on the region. We observed no evidence of northward tree migration. An increase in the areal extent of burned forests, mostly in areas south of the forest-tundra, was the largest change detected. We documented systematic discrepancies between our tree cover estimates and GFC data. GFC underestimates of tree cover typically occurred in areas of low tree density. Areas where GFC data overestimated tree cover were common, especially near the northern limits of trees and in areas dominated by dense or tall shrubs. Predictions of climate-driven vegetation response derived solely from remotely sensed data may not be reliable.

Holocene Critical Zone dynamics in an Alpine catchment inferred from a speleothem multiproxy record: disentangling climate and human influences

Disentangling the effects of climate and human impact on the long-term evolution of the Earth Critical Zone is crucial to understand the array of its potential responses to the ongoing Global Change. This task requires natural archives from which local information about soil and vegetation can be linked directly to climate parameters. Here we present a high-resolution, well-dated, speleothem multiproxy record from the SW Italian Alps, spanning the last ~10,000 years of the present interglacial (Holocene). We correlate magnetic properties and the carbon stable isotope ratio to soil stability and pedogenesis, whereas the oxygen isotope composition is interpreted as primarily related to precipitation amount, modulated at different timescales by changes in precipitation source and seasonality. During the 9.7-2.8 ka period, when anthropic pressure over the catchment was scarce, intervals of enhanced soil erosion are related to climate-driven vegetation contractions and occurred during drier periods. Immediately following the onset of the Iron Age (ca. 2.8 ka), by contrast, periods of enhanced soil erosion coincided with a wetter climate. We propose that the observed changes in the soil response to climate forcing were related to early anthropogenic manipulations of Earth’s surface, which made the ECZ more sensitive to climate oscillations.

A climate-change vulnerability and adaptation assessment for Brazil's protected areas.

Brazil hosts the largest expanse of tropical ecosystems within protected areas (PAs), which shelter biodiversity and support traditional human populations. We assessed the vulnerability to climate change of 993 terrestrial and coastal-marine Brazilian PAs by combining indicators of climatic-change hazard with indicators of PA resilience (size, native vegetation cover, and probability of climate-driven vegetation transition). This combination of indicators allows the identification of broad climate-change adaptation pathways. Seventeen PAs (20,611 km2 ) were highly vulnerable and located mainly in the Atlantic Forest (7 PAs), Cerrado (6), and the Amazon (4). Two hundred fifty-eight PAs (756,569 km2 ), located primarily in Amazonia, had a medium vulnerability. In the Amazon and western Cerrado, the projected severe climatic change and probability of climate-driven vegetation transition drove vulnerability up, despite the generally good conservation status of PAs. Over 80% of PAs of high or moderate vulnerability are managed by indigenous populations. Hence, besides the potential risks to biodiversity, the traditional knowledge and livelihoods of the people inhabiting these PAs may be threatened. In at least 870 PAs, primarily in the Atlantic Forest and Amazon, adaptation could happen with little or no intervention due to low climate-change hazard, high resilience status, or both. At least 20 PAs in the Atlantic Forest, Cerrado, and Amazonia should be targeted for stronger interventions (e.g., improvement of ecological connectivity), given their low resilience status. Despite being a first attempt to link vulnerability and adaptation in Brazilian PAs, we suggest that some of the PAs identified as highly or moderately vulnerable should be prioritized for testing potential adaptation strategies in the near future.

Could plant diversity metrics explain climate-driven vegetation changes on mountain summits of the GLORIA network?

High-elevation habitats host a large number of plant species and are characterized by high biodiversity. The vegetation dynamics in these cold adapted ecosystems are difficult to predict, being affected by global warming, especially in the last decades. With the aim to promote a better understanding of climate-driven changes of alpine vegetation, we investigated the variation in species richness, α-diversity, β-diversity, and total cover of plant functional types over a time lapse of 15 years, relying on multiple re-surveys of mountain summit vegetation in 2001, 2008 and 2015. The study area, included in the long term global observation network GLORIA, was at the boundary between temperate and Mediterranean mountains of S-Europe (northern Apennines, Italy). We identified a trend of loss in biodiversity and signals of biotic homogenization using multiple diversity metrics, despite the overall species richness increment observed in the study area. Cold-adapted and rare species declined while dominant species like graminoids and shrubs increased. Our results highlight that long-term vegetation monitoring activities paired with multiple measures of diversity are required to properly assess biodiversity and to obtain useful indications for future conservation activities in alpine environments. The methods here presented could be applied in all GLORIA sites to quantify biodiversity changes over time, obtaining comparable results for biodiversity monitoring in high-elevation habitats from all over the world.

Assessment of Climate Change and Associated Vegetation Cover Change on Watershed-Scale Runoff and Sediment Yield

Climate change has an important impact on water balance and material circulation in watersheds. Quantifying the influence of climate and climate-driven vegetation cover changes on watershed-scale runoff and sediment yield will help to deepen our understanding of the environmental effects of climate change. Taking the Zhenjiangguan Watershed in Sichuan Province, China as a case study, three downscaled general circulation models with two emission scenarios were used to generate possible climatic conditions for three future periods of P1 (2020–2039), P2 (2050–2069) and P3 (2080–2099). Differences in scenarios were compared with the base period 1980–1999. Then, a Normalized Difference Vegetation Index climate factor regression model was established to analyze changes to vegetation cover under the climate change scenarios. Finally, a Soil and Water Assessment Tool model was built to simulate the response of runoff and sediment yield in the three future periods under two different scenarios: only changes in climate and synergistic changes in climate and vegetation cover. The temperature and precipitation projections showed a significant increasing trend compared to the baseline condition for both emission scenarios. Climate change is expected to increase the average annual runoff by 15%–38% compared with the base period, and the average annual sediment yield will increase by 4%–32%. The response of runoff and sediment yield varies in different periods, scenarios, and sub-watersheds. Climate-driven vegetation cover changes have an impact on runoff and sediment yield in the watershed, resulting in a difference of 5.8%–12.9% to the total changes. To some extent, the changes in vegetation cover will inhibit the hydrological impact of climate changes. The study helps to clarify the effects of climate and vegetation cover factors on hydrological variations in watersheds and provides further support for understanding future hydrological scenarios and implementing effective protection and use of water and soil resources.

Shifting landscapes: decoupled urban irrigation and greenness patterns during severe drought

Urban outdoor water conservation and efficiency offer high potential for demand-side management, but irrigation, greenness, and climate interlinks must be better understood to design optimal policies. To identify paired transitions during drought, we matched parcel-level water use data from smart, dedicated irrigation meters with high-spatial resolution, multispectral aerial imagery. We examined changes across 72 non-residential parcels using potable or recycled water for large landscape irrigation over four biennial summers (2010, 2012, 2014, and 2016) that encompassed a historic drought in California. We found that despite little change in irrigation levels during the first few years of the drought, parcel greenness deteriorated. Between summers 2010 and 2014, average parcel greenness decreased −61% for potable water irrigators and −56% for recycled water irrigators, providing evidence that vegetation could not reach its vigor from wetter, cooler years as the drought intensified with abnormally high temperatures. Between summers 2014–2016 as drought severity lessened, irrigation rates decreased significantly in line with high drought saliency, but greenness rebounded ubiquitously, on average +110% for potable water irrigators and +62% for recycled water irrigators, demonstrating climate-driven vegetation recovery as evaporation and plant evapotranspiration rates decreased. Transitions were similar for customers with both potable and recycled water; vegetation changes were dominated by the overarching climatic regime. As irrigation cannot always overcome drought conditions, which will become more severe under climate change, to maintain vegetation health, utilities and urban planners should consider the tradeoffs between providing green spaces and water scarcity. This includes evaluating the roles of climate-appropriate landscaping and adaptive reallocation of potable and recycled water resources to enhance water security. By addressing emerging themes in urban water management through analysis of data from forthcoming water metering and aerial imagery technologies, this research provides a unique perspective on water use, greenness, and drought linkages.

A rapid method for quantifying landscape-scale vegetation disturbances by surface coal mining in arid and semiarid regions

Quantifying landscape-scale vegetation disturbances by surface coal mining (SCM) is crucial for assessing and mitigating its negative impacts on the environment. Methods for detecting such disturbances in woody ecosystems exist, but these methods do not work well for deserts and grasslands in arid and semiarid regions because of their sensitive responses to precipitation variations. The objective of this study was to develop a new index to reliably detect the locations and spatial extents of SCM-induced vegetation disturbances in dryland regions in the face of fluctuating precipitation. We have developed a vegetation disturbance index (VDI) that combines MODIS EVI data with precipitation data to detect vegetation disturbances by SCM on the Mongolian Plateau during 2000–2015. The VDI is computed by comparing vegetation production per unit precipitation for a given year with a multi-year mean, and by considering distances from coal-mining areas. Our results show that the VDI was able to adequately distinguish vegetation disturbances by SCM from climate-driven vegetation changes in five selected sites across the Mongolian Plateau. The VDI provides an effective tool for quantifying the locations, spatial extents, and severity of vegetation disturbances by SCM in arid and semiarid regions.

Tropical climate–vegetation–fire relationships: multivariate evaluation of the land surface model JSBACH

Abstract. The interactions between climate, vegetation and fire can strongly influence the future trajectories of vegetation in Earth system models. We evaluate the relationships between tropical climate, vegetation and fire in the global vegetation model JSBACH, using a simple fire scheme and the complex fire model SPITFIRE with the aim to identify potential for model improvement. We use two remote-sensing products (based on MODIS and Landsat) in different resolutions to assess the robustness of the obtained observed relationships. We evaluate the model using a multivariate comparison that allows us to focus on the interactions between climate, vegetation and fire and test the influence of land use change on the modelled patterns. Climate–vegetation–fire relationships are known to differ between continents; we therefore perform the analysis for each continent separately. The observed relationships are similar in the two satellite data sets, but maximum tree cover is reached at higher precipitation values for coarser resolution. This shows that the spatial scale of models and data needs to be consistent for meaningful comparisons. The model captures the broad spatial patterns with regional differences, which are partly due to the climate forcing derived from an Earth system model. Compared to the simple fire scheme, SPITFIRE strongly improves the spatial pattern of burned area and the distribution of burned area along increasing precipitation. The correlation between precipitation and tree cover is higher in the observations than in the largely climate-driven vegetation model, with both fire models. The multivariate comparison identifies excessive tree cover in low-precipitation areas and a too-strong relationship between high fire occurrence and low tree cover for the complex fire model. We therefore suggest that drought effects on tree cover and the impact of burned area on tree cover or the adaptation of trees to fire can be improved. The observed variation in the relationship between precipitation and maximum tree cover between continents is higher than the simulated one. Land use contributes to the intercontinental differences in fire regimes with SPITFIRE and strongly overprints the modelled multimodality of tree cover with SPITFIRE. The multivariate model–data comparison used here has several advantages: it improves the attribution of model–data mismatches to model processes, it reduces the impact of biases in the meteorological forcing on the evaluation and it allows us to evaluate not only a specific target variable but also the interactions.