Landscape Partnership Resources Library
Plant-Pollinator Interactions over 120 Years: Loss of Species, Co-Occurrence, and Function
Using historic data sets, we quantified the degree to which global change over 120 years disrupted plant-pollinator interactions in a temperate forest understory community in Illinois, USA. We found degradation of interaction network structure and function and extirpation of 50% of bee species. Network changes can be attributed to shifts in forb and bee phenologies resulting in temporal mismatches, nonrandom species extinctions, and loss of spatial co-occurrences between extant species in modified landscapes. Quantity and quality of pollination services have declined through time. The historic network showed flexibility in response to disturbance; however, our data suggest that networks will be less resilient to future changes.
Gus Speth: Communicating environmental risks in an age of disinformation
Once described as "the consummate environmental insider," Gus Speth, co-founder of the Natural Resources Defense Council, says that green organizations, politicians, and the media are failing to address the root causes of climate change and other environmental problems. He points the finger at what he calls the Òeconomic growth imperativeÓÑthe incessant quest for wealth by corporations, governments, and individualsÑand argues for decou- pling job growth from economic growth. Speth envisions a post-growth society in which renewable energy plays an important role, but the emphasis is on improved efficiency: an energy-sipping, rather than an energy-guzzling, society. He reflects on the politicization and polarization that destroyed a national consensus for action on climate change. Speth urges environmental groups not to settle for meager progress in Washington, but rather to challenge the political system and to build broad coalitions with groups working for social justice and political reform. climate change, economic growth, energy efficiency, environmental groups, environmental law, post-growth society, renewable energy, social justice
Microbes on mountainsides: Contrasting elevational patterns of bacterial and plant diversity
The study of elevational diversity gradients dates back to the foundation of biogeography. Although elevational patterns of plant and animal diversity have been studied for centuries, such patterns have not been reported for microorganisms and remain poorly understood. Here, in an effort to assess the generality of elevational diversity patterns, we examined soil bacterial and plant diversity along an elevation gradient. To gain insight into the forces that structure these patterns, we adopted a multifaceted approach to incorporate information about the structure, diversity, and spatial turnover of montane communities in a phylogenetic context. We found that observed patterns of plant and bacterial diversity were fundamentally different. While bacterial taxon richness and phylogenetic diversity decreased monotonically from the lowest to highest elevations, plants followed a unimodal pattern, with a peak in richness and phylogenetic diversity at mid-elevations. At all elevations bacterial communities had a tendency to be phylogenetically clustered, containing closely re- lated taxa. In contrast, plant communities did not exhibit a uniform phylogenetic structure across the gradient: they became more overdispersed with increasing elevation, containing distantly re- lated taxa. Finally, a metric of phylogenetic beta-diversity showed that bacterial lineages were not randomly distributed, but rather exhibited significant spatial structure across the gradient, whereas plant lineages did not exhibit a significant phylogenetic signal. Quantifying the influence of sample scale in intertaxonomic com- parisons remains a challenge. Nevertheless, our findings suggest that the forces structuring microorganism and macroorganism communities along elevational gradients differ. elevation gradient microbial ecology phylogenetic diversity macroecology biogeography
Regional vegetation die-off in response to global-change-type drought
uture drought is projected to occur under warmer temperature conditions as climate change progresses, referred to here as global- change-type drought, yet quantitative assessments of the triggers and potential extent of drought-induced vegetation die-off remain pivotal uncertainties in assessing climate-change impacts. Of par- ticular concern is regional-scale mortality of overstory trees, which rapidly alters ecosystem type, associated ecosystem properties, and land surface conditions for decades. Here, we quantify region- al-scale vegetation die-off across southwestern North American woodlands in 2002–2003 in response to drought and associated bark beetle infestations. At an intensively studied site within the region, we quantified that after 15 months of depleted soil water content, >90% of the dominant, overstory tree species (Pinus edulis, a pin ̃on) died. The die-off was reflected in changes in a remotely sensed index of vegetation greenness (Normalized Dif- ference Vegetation Index), not only at the intensively studied site but also across the region, extending over 12,000 km2 or more; aerial and field surveys confirmed the general extent of the die-off. Notably, the recent drought was warmer than the previous sub- continental drought of the 1950s. The limited, available observa- tions suggest that die-off from the recent drought was more extensive than that from the previous drought, extending into wetter sites within the tree species’ distribution. Our results quantify a trigger leading to rapid, drought-induced die-off of overstory woody plants at subcontinental scale and highlight the potential for such die-off to be more severe and extensive for future global-change-type drought under warmer conditions. tree mortality vegetation dynamics climate change impacts woodlands Pinus edulis
Vegetation synchronously leans upslope as climate warms
Ecologists have long sought to understand how vegetation re- lates to climate (1, 2). Such knowledge underlies effective mitigation and adaptation to contempo- rary climate change (3). Warming tem- peratures associated with anthropogenic increases in greenhouse gases have led ecologists to predict that vegetation gra- dients will ‘‘march’’ up the hill as cli- mate envelopes shift with elevation, at a lag that scales with species’ generation times (4, 5). This prediction derives from the hypothesis that low-temperature constraints relax in association with warming climate, resulting in more fa- vorable conditions for establishment and growth at the leading edge of a species’ range (e.g., the upper elevation bound- ary on a mountain) (6, 7). Because of competition and change in plant-available water, the trailing edge is expected to track the leading edge (5) with the cen- tral tendency expected to concurrently ‘‘march’’ upslope. This type of response has important implications for predict- ing and mitigating climate change impacts, particularly for vegetation span- ning elevation gradients. If, rather than collectively moving with climate change, responses of dominant species assem- bled along an elevation gradient are highly individualistic, there is greater potential for more novel, nonanalog veg- etation assemblages.
Global evidence that deforestation amplifies flood risk and severity in the developing world
With the wide acceptance of forest-protection policies in the developing world comes a requirement for clear demonstrations of how deforestation may erode human well-being and economies. For centuries, it has been believed that forests provide protection against flooding. However, such claims have given rise to a heated polemic, and broad-scale quantitative evidence of the possible role of forests in flood protection has not been forthcoming. Using data collected from 1990 to 2000 from 56 developing countries, we show using generalized linear and mixed-effects models contrasted with information- theoretic measures of parsimony that flood frequency is negatively correlated with the amount of remaining natural forest and positively correlated with natural forest area loss (after controlling for rainfall, slope and degraded landscape area). The most parsimo- nious models accounted for over 65% of the variation in flood frequency, of which nearly 14% was due to forest cover variables alone. During the decade investigated, nearly 100 000 people were killed and 320 million people were displaced by floods, with total reported economic damages exceeding US$1151 billion. Extracted measures of flood severity (flood duration, people killed and displaced, and total damage) showed some weaker, albeit detectable correlations to natural forest cover and loss. Based on an arbitrary decrease in natural forest area of 10%, the model-averaged prediction of flood frequency increased between 4% and 28% among the countries modeled. Using the same hypothetical decline in natural forest area resulted in a 4–8% increase in total flood duration. These correlations suggest that global-scale patterns in mean forest trends across countries are meaningful with respect to flood dynamics. Unabated loss of forests may increase or exacerbate the number of flood-related disasters, negatively impact millions of poor people, and inflict trillions of dollars in damage in disadvantaged economies over the coming decades. This first global-scale empirical demonstration that forests are correlated with flood risk and severity in developing countries reinforces the imperative for large-scale forest protection to protect human welfare, and suggests that reforestation may help to reduce the frequency and severity of flood-related catastrophes. Keywords: conservation, damage, flooding events, forest loss, generalized linear mixed-effects models, generalized linear models, human displacement, projected costs, rainfall
Thriving Arctic Bottom Dwellers Could Get Strangled by Warming
Many biologists hypothesize that climate change could hurt the Arctic benthos and the large creatures that live off it by wiping out ice (and hence ice algae), lengthening growing seasons for zooplankton, and giving warm- water species a foothold. “The way the system works now is very much in favor of the benthos,” says UAF polar ecologist Rolf Gradinger. “If the sys- tem changes, things could go downhill fast.”
The Evolution and Distribution of Species Body Size
The distribution of species body size within taxonomic groups exhibits a heavy right tail extending over many orders of magnitude, where most species are much larger than the smallest species. We provide a simple model of cladogenetic diffusion over evolutionary time that omits explicit mechanisms for interspecific competition and other microevolutionary processes, yet fully explains the shape of this distribution. We estimate the model’s parameters from fossil data and find that it robustly reproduces the distribution of 4002 mammal species from the late Quaternary. The observed fit suggests that the asymmetric distribution arises from a fundamental trade-off between the short-term selective advantages (Cope’s rule) and long-term selective risks of increased species body size in the presence of a taxon-specific lower limit on body size
Grassland Vegetation Changes and Nocturnal Global Warming
Global minimum temperatures (TMIN) are increasing faster than maximum temperatures, but the ecological consequences of this are largely unexplored. Long-term data sets from the shortgrass steppe were used to identify corre- lations between TMIN and several vegetation variables. This ecosystem is po- tentially sensitive to increases in TMIN. Most notably, increased spring TMIN was correlated with decreased net primary production by the dominant C4 grass (Bouteloua gracilis) and with increased abundance and production by exotic and native C3 forbs. Reductions in B. gracilis may make this system more vulnerable to invasion by exotic species and less tolerant of drought and grazing.
Integrating multiple lines of evidence into historical biogeography hypothesis testing: a Bison bison case study
One of the grand goals of historical biogeography is to understand how and why species’ population sizes and distributions change over time. Multiple types of data drawn from disparate fields, combined into a single modelling framework, are necessary to document changes in a species’s demography and distribution, and to determine the drivers responsible for change. Yet truly integrated approaches are challenging and rarely performed. Here, we discuss a modelling framework that integrates spatio-temporal fossil data, ancient DNA, palaeoclimatological reconstruc- tions, bioclimatic envelope modelling and coalescence models in order to statistically test alternative hypotheses of demographic and potential distri- butional changes for the iconic American bison (Bison bison). Using different assumptions about the evolution of the bioclimatic niche, we generate hypothetical distributional and demographic histories of the species. We then test these demographic models by comparing the genetic signature pre- dicted by serial coalescence against sequence data derived from subfossils and modern populations. Our results supported demographic models that include both climate and human-associated drivers of population declines. This synthetic approach, integrating palaeoclimatology, bioclimatic envel- opes, serial coalescence, spatio-temporal fossil data and heterochronous DNA sequences, improves understanding of species’ historical biogeography by allowing consideration of both abiotic and biotic interactions at the population level
Global Biodiversity Conservation and the Alleviation of Poverty
Poverty and biodiversity loss are two of the world’s dire challenges. Claims of conservation’s contribution to poverty alleviation, however, remain controversial. Here, we assess the flows of ecosystem services provided to people by priority habitats for terrestrial conservation, considering the global distributions of biodiversity, physical factors, and socioeconomic context. We estimate the value of these habitats to the poor, both through direct benefits and through payments for ecosystem services to those stewarding natural habitats. The global potential for biodiversity conservation to support poor communities is high: The top 25% of conservation priority areas could provide 56%–57% of benefits. The aggregate benefits are valued at three times the estimated opportunity costs and exceed $1 per person per day for 331 million of the world’s poorest people. Although trade-offs remain, these results show win–win synergies between conservation and poverty alleviation, indicate that effective financial mecha- nisms can enhance these synergies, and suggest biodiversity conservation as a fundamental component of sustainable economic development. Keywords: ecosystem service flows, poverty alleviation, biodiversity conservation priorities, natural capital, valuation
The bigger they come, the harder they fall: body size and prey abundance influence predator −prey ratios
Large carnivores are highly threatened, yet the processes underlying their population declines are still poorly understood and widely debated. We explored how body mass and prey abundance influence carnivore density using data on 199 populations obtained across multiple sites for 11 carnivore species. We found that relative decreases in prey abundance resulted in a five- to sixfold greater decrease in the largest carnivores compared with the smallest species. We discuss a number of possible causes for this inherent vulnerability, but also explore a possible mechanistic link between predator size, ener- getics and population processes. Our results have important implications for carnivore ecol- ogy and conservation, demonstrating that larger species are particularly vulnerable to anthropo- genic threats to their environment, especially those which have an adverse affect on the abundance of their prey. Keywords: carnivore ecology; predator–prey relationships; abundance scaling; climate change; metabolism
Predicting ecosystem shifts requires new approaches that integrate the effects of climate change across entire systems
Most studies that forecast the ecological conse- quences of climate change target a single species and a single life stage. Depending on climatic impacts on other life stages and on interacting species, however, the results from simple exper- iments may not translate into accurate predictions of future ecological change. Research needs to move beyond simple experimental studies and environmental envelope projections for single species towards identifying where ecosystem change is likely to occur and the drivers for this change. For this to happen, we advocate research directions that (i) identify the critical species within the target ecosystem, and the life stage(s) most susceptible to changing conditions and (ii) the key interactions between these species and components of their broader ecosystem. A combined approach using macroecology, experimentally derived data and modelling that incorporates energy budgets in life cycle models may identify critical abiotic conditions that disproportionately alter important ecological processes under forecasted climates. Keywords: climate change; ocean acidification; global warming; species interactions; ecosystem shift; productivity and consumption
How global extinctions impact regional biodiversity in mammals
Phylogenetic diversity (PD) represents the evol- utionary history of a species assemblage and is a valuable measure of biodiversity because it cap- tures not only species richness but potentially also genetic and functional diversity. Preserving PD could be critical for maintaining the func- tional integrity of the world’s ecosystems, and species extinction will have a large impact on ecosystems in areas where the ecosystem cost per species extinction is high. Here, we show that impacts from global extinctions are linked to spatial location. Using a phylogeny of all mam- mals, we compare regional losses of PD against a model of random extinction. At regional scales, losses differ dramatically: several biodiversity hotspots in southern Asia and Amazonia will lose an unexpectedly large proportion of PD. Global analyses may therefore underestimate the impacts of extinction on ecosystem processes and function because they occur at finer spatial scales within the context of natural biogeography. Keywords: phylogenetic diversity; biodiversity; threatened species; mammals; extinction
On the vapour trail of an atmospheric imprint in insects
Terrestrial arthropods, at constant risk from desiccation, are highly sensitive to atmospheric temperature and humidity. A physiological marker of these abiotic conditions could highlight phenotypic adaptations, indicate niche partitioning, and predict responses to climate change for a group representing three-quarters of the Earth’s animal species. We show that the 18O composition of insect haemolymph is such a measure, providing a dynamic and quantitatively predictable signal for respiratory gas exchange and inputs from atmospheric humidity. Using American cockroaches (Periplaneta americana) under defined experimental conditions, we show that insects respiring at low humidity demon- strate the expected enrichment in the 18O composition of haemolymph because of evapor- ation. At high humidity, however, diffusional influx of atmospheric water vapour into the animal forces haemolymph to become depleted in 18O. Additionally, using cockroaches sampled from natural habitats, we show that the haemo- lymph 18O signature is transferred to the organic material of the insect’s exoskeleton. Insect cuticle, therefore, exhibits the mean atmospheric conditions surrounding the animals prior to moulting. This discovery will help to define the climatic tolerances of species and their habitat preferences, and offers a means of quantifying the balance between niche partitioning and ‘neutral’ processes in shaping complex tropical forest communities. Keywords: stable isotopes; arthropods; niches; neutral theory; climate change
The evolution of growth rates on an expanding range edge
Individuals in the vanguard of a species invasion face altered selective conditions when compared with conspecifics behind the invasion front. Assortment by dispersal ability on the expanding front, for example, drives the evolution of increased dispersal, which, in turn, leads to accel- erated rates of invasion. Here I propose an additional evolutionary mechanism to explain accelerating invasions: shifts in population growth rate (r). Because individuals in the van- guard face lower population density than those in established populations, they should (relative to individuals in established populations) experience greater r-selection. To test this possibility, I used the ongoing invasion of cane toads (Bufo marinus) across northern Australia. Life-history theory shows that the most efficient way to increase the rate of population growth is to reproduce earlier. Thus, I predict that toads on the invasion front will exhibit faster individual growth rates (and thus will reach breeding size earlier) than those from older populations. Using a common garden design, I show that this is indeed the case: both tadpoles and juvenile toads from frontal popu- lations grow around 30 per cent faster than those from older, long established populations. These results support theoretical predictions that r increases during range advance and highlight the importance of understanding the evolution of life history during range advance. Keywords: Bufo marinus; invasive species; Rhinella marina; r-selection
Modelling the long-term response to positive and negative priming of soil organic carbon by black carbon
bserved increases in the mineralization rate of labile organic carbon (LOC) in the presence of black carbon (BC) have led to speculation that corresponding decreases in non-pyrogenic (i.e. non- BC) soil organic carbon (npSOC) could significantly reduce or negate the C sequestration benefit of BC in soils. Here we show that the potential effect of an increased LOC decomposition rate on long-term npSOC stocks is negligible, even when using assump- tions that would favour large losses, potentially causing no more than 3–4 % loss of npSOC over 100 years if 50 % of above-ground crop residues were converted to BC annually. Conversely, if the BC- stimulated enhanced stabilization of npSOC that has been observed in laboratory trials is extrapolated to the long-term, it would greatly increase soil carbon stocks by 30–60 %. Annual additions of BC derived from crop residues would increase total SOC (including both BC and npSOC) by an amount five times greater than the potential increase from enhanced stabilization and an order of magnitude greater than losses of npSOC caused by annual removals of biomass to provide BC feedstock. Keywords Black carbon Soil organic carbon Terrestrial carbon cycle Fire Biochar
Water and bioenergy
Water management expert Arjen Hoekstra, together with environmental science and energy specialists, has analysed the impact of increasing the use of biofuels in the transport sector on global water demand.
Impacts of Climate Change on Biodiversity, Ecosystems, and Ecosystem Services Technical Input to the 2013 National Climate Assessment
KEY FINDINGS Biodiversity and ecosystems are already more stressed than at any comparable period of human history. Climate change almost always exacerbates the problems caused by other environmental stressors including: land use change and the consequent habitat fragmentation and degradation; extraction of timber, fish, water, and other resources; biological disturbance such as the introduction of non-native invasive species, disease, and pests; and chemical, heavy metal, and nutrient pollution. As a corollary, one mechanism for reducing the negative impacts of climate change is a reduction in other stressors. Climate change is causing many species to shift their geographical ranges, distributions, and phenologies at faster rates than previously thought. Changes in terrestrial plant and animal species ranges are shifting the location and extent of biomes, and altering ecosystem structure and functioning. These rates vary considerably among species. Terrestrial species are moving up in elevation at rates 2 to 3 times greater than initial estimates. Despite faster rates of warming in terrestrial systems compared to ocean environments, the velocity of range shifts for marine taxa exceeds those reported for terrestrial species. Species and populations that are unable to shift their geographic distributions or have narrow environmental tolerances are at an increased risk of extinction. There is increasing evidence of population declines and localized extinctions that can be directly attributed to climate change. Ecological specialists and species that live at high altitudes and latitudes are particularly vulnerable to climate change. Overall, the impacts of climate change are projected to result in a net loss of global biodiversity and major shifts in the provision of ecosystem services. For example, the range and abundance of economically important marine fish are already changing due to climate change and are projected to continue changing such that some local fisheries are very likely to cease to be viable, whereas others may become more valuable if the fishing community can adapt. Range shifts will result in new community assemblages, new associations among species, and promote interactions among species that have not existed in the past. Changes in the spatial distribution and seasonal timing of flora and fauna within marine, aquatic, and terrestrial environments can result in trophic mismatches and asynchronies. Novel species assemblages can also substantially alter ecosystem structure and function and the distribution of ecosystem services. Changes in precipitation regimes and extreme events can cause ecosystem transitions, increase transport of nutrients and pollutants to downstream ecosystems, and overwhelm the ability of natural systems to mitigate harm to people from these events. Changes in extreme events affect systems differentially, because different thresholds are crossed. For example, more intense storms and increased drought coupled with warming can shift grasslands into shrublands, or facilitate domination by other grass types (for example, mixed grass to C-4 tallgrass). More heavy rainfall also increases movement of nutrients and pollutants to downstream ecosystems, restructuring processes, biota, and habitats. As a consequence, regulation of drinking water quality is very likely to be strained as high rainfall and river discharge lead to higher levels of nitrogen in rivers and greater risk of waterborne disease outbreaks. S-2 Impacts of Climate Change on Biodiversity, Ecosystems, and Ecosystem Services | Executive Summary Technical Input to the 2013 National Climate Assessment Changes in winter have big and surprising effects on ecosystems and their services. Changes in soil freezing, snow cover, and air temperature have affected carbon sequestration, decomposition, and carbon export, which influence agricultural and forest production. Seasonally snow-covered regions are especially susceptible to climate change as small changes in temperature or precipitation may result in large changes in ecosystem structure and function. Longer growing seasons and warmer winters are enhancing pest outbreaks, leading to tree mortality and more intense and extensive fires. For winter sports and recreation, future economic losses are projected to be high because of decreased or unreliable snowfall. The ecosystem services provided by coastal habitats are especially vulnerable to sea-level rise and more severe storms. The Atlantic and Gulf of Mexico coasts are most vulnerable to the loss of coastal protection services provided by wetlands and coral reefs. Along the Pacific coast long-term erosion of dunes due to increasing wave heights is projected to be an increasing problem for coastal communities. Beach recreation is also projected to suffer due to coastal erosion. Other forms of recreation are very likely to improve due to better weather, and the net effect is likely a redistribution of the industry and its economic impact, with visitors and tourism dollars shifting away from some communities in favor of others. Climate adaptation has experienced a dramatic increase in attention since the last National Climate Assessment and become a major emphasis in biodiversity conservation and natural resource policy and management. Federal and State agencies are planning for and integrating climate change research into resource management and actions to address impacts of climate change based on historical impacts, future vulnerabilities, and observations on the ground. Land managers have realized that static protected areas will not be sufficient to conserve biodiversity in a changing climate, requiring an emphasis on landscape-scale conservation, connectivity among protected habitats, and sustaining ecological functioning of working lands and waters. Agile and adaptive management approaches are increasingly under development, including monitoring, experimentation, and a capacity to evaluate and modify management actions. Risk-based framing and stakeholder-driven scenario planning will be essential in enhancing our ability to respond to the impacts of climate change. Climate change responses employed by other sectors (for example, energy, agriculture, transportation) are creating new ecosystem stresses, but also can incorporate ecosystem- based approaches to improve their efficacy. Ecosystem-based adaptation has emerged as a framework for understanding the role of ecosystem services in moderating climate impacts on people, although this concept is currently being used more on an international scale than within the United States. Ecological monitoring efforts need to be improved and better coordinated among Federal and State agencies to ensure that the impacts of climate change are adequately observed as well as to support ecological research, management, assessment, and policy. As species and ecosystem boundaries shift to keep pace with climate change, improved and better-integrated research, monitoring, and assessment efforts will be needed at national and global scales. Existing monitoring networks in the United States are not well suited for detecting and attributing the impacts of climate change to the wide range of affected species at the appropriate spatio-temporal scales.
Toward a Global Biodiversity Observing System
Tracking biodiversity change is increasingly important in sustaining ecosystems and ultimately human well-being.
