Scenarios for Global Biodiversity in the 21st Century Pereira, Henrique M.; Leadley, Paul W.; Proença, Vânia ...
Science (American Association for the Advancement of Science),
12/2010, Letnik:
330, Številka:
6010
Journal Article
Recenzirano
Odprti dostop
Quantitative scenarios are coming of age as a tool for evaluating the impact of future socioeconomic development pathways on biodiversity and ecosystem services. We analyze global terrestrial, ...freshwater, and marine biodiversity scenarios using a range of measures including extinctions, changes in species abundance, habitat loss, and distribution shifts, as well as comparing model projections to observations. Scenarios consistently indicate that biodiversity will continue to decline over the 21st century. However, the range of projected changes is much broader than most studies suggest, partly because there are major opportunities to intervene through better policies, but also because of large uncertainties in projections.
Semi-arid areas, defined as those areas of the world where water is an important limitation for plant growth, have become the subject of increased interest due to the impacts of current global ...changes and sustainability of human lifestyles. While many ground-based reports of declining vegetation productivity have been published over the last decades, a number of recent publications have shown a nuanced and, for some regions, positive picture. With this background, the paper provides an analysis of trends in vegetation greenness of semi-arid areas using AVHRR GIMMS from 1981 to 2007. The vegetation index dataset is used as a proxy for vegetation productivity and trends are analyzed for characterization of changes in semi-arid vegetation greenness. Calculated vegetation trends are analyzed with gridded data on potential climatic constraints to plant growth to explore possible causes of the observed changes. An analysis of changes in the seasonal variation of vegetation greenness and climatic drivers is conducted for selected regions to further understand the causes of observed inter-annual vegetation changes in semi-arid areas across the globe. It is concluded that semi-arid areas, across the globe, on average experience an increase in greenness (0.015 NDVI units over the period of analysis). Further it is observed that increases in greenness are found both in semi-arid areas where precipitation is the dominating limiting factor for plant production (0.019 NDVI units) and in semi-arid areas where air temperature is the primarily growth constraint (0.013 NDVI units). Finally, in the analysis of changes in the intra-annual variation of greenness it is found that seemingly similar increases in greenness over the study period may have widely different explanations. This implies that current generalizations, claiming that land degradation is ongoing in semi-arid areas worldwide, are not supported by the satellite based analysis of vegetation greenness.
► Trends in dryland vegetation greenness (NDVI) based on AVHRR data are analyzed. ► Climatic constraints to plant growth are anlysed to study causes of NDVI changes. ► Global drylands on average experience an increase in NDVI from 1981 to 2007. ► Trends have regional specific explanations and generalizations are not supported.
Dust Unto Dust Scholes, Mary C.; Scholes, Robert J.
Science (American Association for the Advancement of Science),
11/2013, Letnik:
342, Številka:
6158
Journal Article
Recenzirano
In the past, great civilizations have fallen because they failed to prevent the degradation of the soils on which they were founded (1). The modern world could suffer the same fate at a global scale. ...The inherent productivity of many lands has been dramatically reduced as a result of soil erosion, accumulation of salinity, and nutrient depletion. In Africa, where much of the future growth in agriculture must take place, erosion has reduced yields by 8% at continental scale (2), and nutrient depletion is widespread (3). Although improved technology-including the unsustainably high use of fertilizers, irrigation, and plowing-provides a false sense of security, about 1% of global land area is degraded every year (4). As Fierer et al. show on page 621 of this issue, the diversity of soil biota in the prairie soils of the American Midwest has changed substantially since cultivation (5). We have forgotten the lesson of the Dust Bowl: Even in advanced economies, human well-being depends on looking after the soil (6). An intact, self-restoring soil ecosystem is essential, especially in times of climate stress.
The regions of the world where average precipitation is between one fifth and half of the potential plant water demand are termed ‘semi-arid’. They make up 15.2% of the global land surface, and the ...approximately 1.1 billion people who live there are among the world’s poorest. The inter-annual variability of rainfall in semi-arid regions is exceptionally high, due to intrinsic features of the global atmospheric circulation. The observed and projected climate trends for most semi-arid regions indicate warming at rates above the global mean rate over land, increasing evaporative demand, and reduced and more variable rainfall. Historically, the ecosystems and people coped with the challenges of semi-arid climates using a range of strategies that are now less viable. Semi-arid ecosystems are by definition water limited, generally only suitable for extensive pastoralism and opportunistic cropping, unless irrigation supplementation is available. The characteristics of dryland plant production in semi-arid ecosystems, as they interact with climate change and human systems, provide a conceptual framework for why land degradation is so conspicuous in semi-arid regions. The coupled social-ecological failures are contagious, both within the landscape and at regional and global scales. Thus, semi-arid lands are a likely flashpoint for Earth system changes in the 21st century.
Understanding the interactions between the multiple ecosystem services (ES) which can be delivered from a single landscape is essential. Most studies on ES relationships use spatial or temporal ...statistical analysis (for example: correlations between services). Methods from microeconomic theory have recently received attention for describing ES relationships. The nature and intensity of ES relationships can be assessed by fitting a production possibility frontier that indicates the maximum amount of one ES that can be produced by landscape, for different levels of another ES. This study estimates production frontiers empirically, and compares the ES relationships insights gained this way with those inferred from correlation approaches. InVEST software was used to model and map the provision of six ES in the Reventazón watershed in Costa Rica. Spatial and temporal ES correlation patterns were analyzed for four observed land uses/land covers (LULC). Production frontiers were constructed using a set of 32 simulated scenarios. Production frontier was the most sensitive method for detecting ES relationships. The nature and intensity of ES relationships revealed depended on the analytic methods used. In comparison with correlations, the production frontier approach provided additional information relating to tradeoff intensity and Pareto efficient LULC configurations.
•The literature applies different methods to assess relationships between ecosystem services•In a case study in Costa Rica, all tested methods showed similar tradeoffs between food and carbon•Methods showed different levels of sensitivity in detecting relationships between services•For most pairs of services, tested methods led to different interpretations, either complementary or contradictory
The challenges of the Anthropocene have forced ecologists into the public space, to contend with issues manifest at scales of tens of kilometers and more, unfolding over decades to centuries. Our ...long fascination with issues of scale is no longer academic. We need to be able to aggregate observations and process understanding derived at the scale of a homogeneous patch to the landscape, region, and the world, and disaggregate changes and limits at the planetary scale to their local outcomes and responses. Several robust approaches to scale-appropriate research and translation in ecology are becoming widely used, but the observation technologies have in some respects outrun both the theory and the general practice for scaling up and scaling down. The project for the next decade is to work simultaneously at multiple scales, using mechanistic, reduced-form, and empirical models to link the scales. The issues related to scale transitions are a manifestation in the spatial and temporal domain of the general problem of ‘emergence,’ which remains suspect in ecology, because it seems to invoke an element of magic. A key challenge for all complex system science, including ecology, is to make the prediction of patterns at one scale from mechanisms operating at different scales into a respectable and reliable practice.
Climate change and ecosystem services Scholes, Robert J.
Wiley interdisciplinary reviews. Climate change,
07/2016, Letnik:
7, Številka:
4
Journal Article
Recenzirano
Studies of the impacts of climate change cover three broad areas: direct effects on humans, their enterprises, and assets; effects on natural systems; and effects on humans via natural systems. ...‘Ecosystem services’ fall into the latter category. Future climates continue to allow ecosystem services to be delivered and consumed, in some cases at a level greater than in the past, and in others degraded relative to their historic supply. Across a wide range of ecosystem services, the losses exceed the gains for magnitudes and rates of climate change projected under low‐mitigation scenarios. On balance, global mean temperature (GMT) rises greater than 2°C above preindustrial have a spatially patchy but net negative effect on many ecosystem services. The negative impacts occur in many places and affect most people. This apparent asymmetry of impact is hypothesized to have three causes: the rapidity of climate change relative to adaptive processes in social and ecological systems; the exposure of societies to climates not experienced during the period over which complex, agriculturally dependent human societies developed; and the approach toward limits in the Earth system. Covariates of climate change—especially rising atmospheric carbon dioxide and ongoing land transformation—are an inextricable part of the projected loss of services in the coming century and the projected shortfall between supply and demand is strongly demand‐driven. The geographical distributions of ecosystem service supply and demand are unequal, and becoming more so. WIREs Clim Change 2016, 7:537–550. doi: 10.1002/wcc.404
This article is categorized under:
Climate, Ecology, and Conservation > Observed Ecological Changes
After photoexcitation, energy absorbed by a molecule can be transferred efficiently over a distance of up to several tens of angstroms to another molecule by the process of resonance energy transfer, ...RET (also commonly known as electronic energy transfer, EET). Examples of where RET is observed include natural and artificial antennae for the capture and energy conversion of light, amplification of fluorescence-based sensors, optimization of organic light-emitting diodes, and the measurement of structure in biological systems (FRET). Forster theory has proven to be very successful at estimating the rate of RET in many donor-acceptor systems, but it has also been of interest to discover when this theory does not work. By identifying these cases, researchers have been able to obtain, sometimes surprising, insights into excited-state dynamics in complex systems. In this article, we consider various ways that electronic energy transfer is promoted by mechanisms beyond those explicitly considered in Forster RET theory. First, we recount the important situations when the electronic coupling is not accurately calculated by the dipole-dipole approximation. Second, we examine the related problem of how to describe solvent screening when the dipole approximation fails. Third, there are situations where we need to be careful about the separability of electronic coupling and spectral overlap factors. For example, when the donors and/or acceptors are molecular aggregates rather than individual molecules, then RET occurs between molecular exciton states and we must invoke generalized Forster theory (GFT). In even more complicated cases, involving the intermediate regime of electronic energy transfer, we should consider carefully nonequilibrium processes and coherences and how bath modes can be shared. Lastly, we discuss how information is obscured by various forms of energetic disorder in ensemble measurements and we outline how single molecule experiments continue to be important in these instances.
SARS-CoV-2 virus infections in humans were first reported in December 2019, the boreal winter. The resulting COVID-19 pandemic was declared by the WHO in March 2020. By July 2020, COVID-19 was ...present in 213 countries and territories, with over 12 million confirmed cases and over half a million attributed deaths. Knowledge of other viral respiratory diseases suggests that the transmission of SARS-CoV-2 could be modulated by seasonally varying environmental factors such as temperature and humidity. Many studies on the environmental sensitivity of COVID-19 are appearing online, and some have been published in peer-reviewed journals. Initially, these studies raised the hypothesis that climatic conditions would subdue the viral transmission rate in places entering the boreal summer, and that southern hemisphere countries would experience enhanced disease spread. For the latter, the COVID-19 peak would coincide with the peak of the influenza season, increasing misdiagnosis and placing an additional burden on health systems. In this review, we assess the evidence that environmental drivers are a significant factor in the trajectory of the COVID-19 pandemic, globally and regionally. We critically assessed 42 peer-reviewed and 80 preprint publications that met qualifying criteria. Since the disease has been prevalent for only half a year in the northern, and one-quarter of a year in the southern hemisphere, datasets capturing a full seasonal cycle in one locality are not yet available. Analyses based on space-for-time substitutions, i.e., using data from climatically distinct locations as a surrogate for seasonal progression, have been inconclusive. The reported studies present a strong northern bias. Socio-economic conditions peculiar to the 'Global South' have been omitted as confounding variables, thereby weakening evidence of environmental signals. We explore why research to date has failed to show convincing evidence for environmental modulation of COVID-19, and discuss directions for future research. We conclude that the evidence thus far suggests a weak modulation effect, currently overwhelmed by the scale and rate of the spread of COVID-19. Seasonally modulated transmission, if it exists, will be more evident in 2021 and subsequent years.
The Pongola Bush Nature Reserve lies in a narrow band along the escarpment between Mpumalanga and KwaZulu-Natal (KZN). Although referred to as ‘bush’, this vegetation type may be considered to fit ...into the intersection of two types of scarp forest: the Northern Afrotemperate Forest and the Southern Mistbelt Forest. The area was heavily logged in the early 1900s with the need for timber for the emerging gold mining industry in Barberton. The forest fragment is now protected but lacks formal tree diversity assessments, and this study sets out to establish its community composition and richness using a range of standard techniques. Distributed throughout the forest, 127 circular plots (each 80 m2) were surveyed. In these, 1152 stems were measured for species, height, and diameter at breast height (DBH). Four species contributed roughly 70% of the 70 Mg ha−1 above ground woody biomass. Stem size class distributions showed a high recruitment rate of small stemmed individuals and few large individuals. This pattern is consistent with the disturbance history of the site, with limited recruitment of certain species, mainly limited to early successional species. The Pongola Bush forest is particularly diverse in terms of tree species: 41 species were recorded, and it is estimated from the species area curve that there may be 70 tree species present.Conservation implications This survey is the first formal tree diversity survey conducted on the Pongola Bush which may assist future research and conservation strategies.
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