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Abstract
Beginning with an overview of how human civilization has altered the face of the Earth, particularly by the destruction of forests, the book details the startling consequences of these actions. Rice provides compelling reasons for government officials, economic leaders, and the public to support efforts to save threatened and endangered plants.
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Tropical deforestation has many consequences, amongst which alteration of the hydrological cycle and loss of habitat and biodiversity
are the focus of much public interest and scientific research. Here we examine the potential biodiversity and hydrological
impacts of an extreme deforestation scenario – the loss of all tropical forest areas currently identified by the World Wildlife
Fund as being threatened. Existing tropical forest areas are first classified according to two categories of biological distinctiveness
– high and low – using indicators developed by the WWF. We apply the tropical deforestation scenario to a macro-scale hydrologic
model, keeping track of the share of change in basin runoff that originates from the deforestation of areas of high versus
low biological distinctiveness and where that change could impact human populations. Of particular interest are those basins
where loss of the most threatened tropical forest areas would give rise to significant biodiversity loss and to potentially large hydrological impacts. In such cases it is conceivable that biodiversity conservation could “free-ride”
on the concerns of resident populations to maintain the forests for the purpose of minimizing hydrological change. Where such
an outcome seems likely, biodiversity conservation efforts might be better targeted elsewhere, perhaps to basins where the
loss of forest areas with high biological distinctiveness would have less population impacts, hence requiring an alliance
between biological and hydrological interests to gain sufficient social and financial support for conservation.
Perennial cropping systems may achieve significant improvement over annual systems in the synchrony between crop nutrient demands and nutrient supplies. Improvements in nutrient synchrony would result in the reduction of nutrient losses and their associated environmental impacts. A perennial system with high levels of synchrony would also require fewer nutrient inputs, such that it may be possible to develop an agriculture that functions mostly, if not entirely, on nutrient inputs from endogenous sources (i.e., weathering of primary and secondary minerals and biological nitrogen fixation). In this paper I describe three realms of research that will inform the development of relatively high-yielding grain production systems grown on endogenous nutrient supplies: (1) improvement of nutrient synchrony through the development of perennial crops; (2) identification of soils that are in a high nutrient release phase of pedogenesis, which could balance the export of rock-derived nutrients in crop harvests; and (3) optimization of legume density, harvest index and percent nitrogen derived from the atmosphere (%Ndfa) to achieve adequate nitrogen inputs through biological fixation.
Alnus maritima and Alnus serrulata are riparian shrubs that occur in similar habitats in the southern and eastern United States. Alnus serrulata is abundant throughout this range, but A. maritima is rare, occurring only in small populations in Oklahoma and Georgia and on the Delmarva Peninsula. Alnus maritima is more resistant than A. serrulata to water and temperature stresses, but the degree to which insolation influences the restricted distribution of A. maritima is unknown. Our goals were to characterize the shade tolerance of A. maritima and A. serrulata and determine whether differences in shade tolerance could help explain the differing ecological success of the two species. Measurements in nature showed that leaves of A. serrulata have greater concentrations of chlorophyll than do leaves of A. maritima, and a greater percentage of A. serrulata inhabit shaded sites. Two experiments evaluating the resistance of seedlings to light-deficit stress revealed that A. maritima had a greater photosynthetic capacity and grew more quickly than A. serrulata in full sunlight. In shade, survival of seedlings was lower and reductions in photosynthesis and growth were greater for A. maritima than for A. serrulata. We conclude that A. serrulata is tolerant and A. maritima is intolerant of shade. Moreover, we conclude that shade intolerance strongly restricts the potential niches of A. maritima within the region where the shade-tolerant A. serrulata is comparatively abundant.
Numerical simulation experiments were conducted to delineate the influence of in situ deforestation data on episodic rainfall by comparing two ensembles of five 5-day integrations performed with a recent version of the Goddard Laboratory for Atmospheres General Circulation Model (GCM) that has a simple biosphere model (SiB). The first set, called control cases, used the standard SiB vegetation cover (comprising 12 biomes) and assumed a fully forested Amazonia, while the second set, called deforestation cases, distinguished the partially deforested regions of Amazonia as savanna. Except for this difference, all other initial and prescribed boundary conditions were kept identical in both sets of integrations. The differential analyses of these five cases show the following local effects of deforestation. (1) A discernible decrease in evapotranspiration of about 0.80 mm/d (roughly 18%) that is quite robust in the averages for 1-, 2-, and 5-day forecasts. (2) A decrease in precipitation of about 1.18 mm/d (roughly 8%) that begins to emerge even in 1-2 day averages and exhibits complex evolution that extends downstream with the winds. (3) A significant decrease in the surface drag force (as a consequence of reduced surface roughness of deforested regions) that, in turn, affects the dynamical structure of moisture convergence and circulation. The surface winds increase significantly during the first day, and thereafter the increase is well maintained even in the 2- and 5-day averages.
Reduced recruitment of blue oak (Quercus douglasii) seedlings in California grasslands and woodlands may result from shifts in seasonal soil water availability coincident with replacement of the native perennial herbaceous community by Mediterranean annuals. We used a combination of container and field experiments to examine the interrelationships between soil water potential, herbaceous neighborhood composition, and blue oak seedling shoot emergence and growth. Neighborhoods of exotic annuals depleted soil moisture more rapidly than neighborhoods of a perennial grass or "no-neighbor" controls. Although effects of neighborhood composition on oak seedling root elongation were not statistically significant, seedling shoot emergence was significantly inhibited in the annual neighborhoods where soil water was rapidly depleted. Seedling water status directly reflected soil water potential, which also determined the extent and duration of oak seedling growth during the first year. End-of-season seedling height significantly influenced survival and growth in subsequent years. While growth and survival of blue oak seedlings may be initially constrained by competition with herbaceous species, subsequent competition with adult blue oak trees may further contribute to reduced sapling recruitment.
Today, the direct and health and environmental costs of wind energy are less than are those of coal energy. The United States could displace 10% of coal energy at no net federal cost by spending 3 to 4% of 1 year's budget on 36,000 to 40,000 large wind turbines and selling the electricity over 20 years. The authors of [this Policy Forum][1] recommend replacing 59% of coal energy with energy from 214,000 to 236,000 turbines, which would allow the United States to meet Kyoto Protocol greenhouse gas targets as of 1999 and simultaneously to improve health, acid deposition, smog, and visibility problems associated with coal.
[1]: http://www.sciencemag.org/cgi/content/full/293/5534/1438
Satellite data show that ice sheets can change much faster than commonly appreciated, with potentially worrying implications
for their stability.
For a scientist studying climate change, 'eureka' moments are unusually rare. Instead progress is generally made by a painstaking piecing together of evidence from every new temperature measurement, satellite sounding or climate-model experiment. Data get checked and rechecked, ideas tested over and over again. Do the observations fit the predicted changes? Could there be some alternative explanation? Good climate scientists, like all good scientists, want to ensure that the highest standards of proof apply to everything they discover. And the evidence of change has mounted as climate records have grown longer, as our understanding of the climate system has improved and as climate models have become ever more reliable. Over the past 20 years, evidence that humans are affecting the climate has accumulated inexorably, and with it has come ever greater certainty across the scientific community in the reality of recent climate change and the potential for much greater change in the future. This increased certainty is starkly reflected in the latest report of the Intergovernmental Panel on Climate Change (IPCC), the fourth in a series of assessments of the state of knowledge on the topic, written and reviewed by hundreds of scientists worldwide. The panel released a condensed version of the first part of the report, on the physical science basis of climate change, in February. Called the 'Summary for Policymakers,' it delivered to policymakers and ordinary people alike an unambiguous message: scientists are more confident than ever that humans have interfered with the climate and that further human-induced climate change is on the way. Although the report finds that some of these further changes are now inevitable, its analysis also confirms that the future, particularly in the longer term, remains largely in our hands--the magnitude of expected change depends on what humans choose to do about greenhouse gas emissions. The physical science assessment focuses on four topics: drivers of climate change, changes observed in the climate system, understanding cause-and-effect relationships, and projection of future changes. Important advances in research into all these areas have occurred since the IPCC assessment in 2001. In the pages that follow, we lay out the key findings that document the extent of change and that point to the unavoidable conclusion that human activity is driving it.
A mature deciduous forest cover in a catchment reduces streamflow compared to a clearcut area. This result has been replicated in many places around the world and is certainly not unique to Coweeta. There is both less quickflow and less baseflow from the forested catchment. Thus, as Charles Hursh correctly surmised, forests in head- water areas provide flood protection for locations further downstream. However, if water resources are scarce, it could be argued that more water could be supplied by clearing the forest. The benefits of increased water supply would have to be set against the increased risk of flooding.
World-renowned canopy biologist Nalini Nadkarni has climbed trees on four continents with scientists, students, artists, clergymen, musicians, activists, loggers, legislators, and Inuits, gathering diverse perspectives. In Between Earth and Sky, a rich tapestry of personal stories, information, art, and photography, she becomes our captivating guide to the leafy wilderness above our heads. Through her luminous narrative, we embark on a multifaceted exploration of trees that illuminates the profound connections we have with them, the dazzling array of goods and services they provide, and the powerful lessons they hold for us. Nadkarni describes trees' intricate root systems, their highly evolved and still not completely understood canopies, their role in commerce and medicine, their existence in city centers and in extreme habitats of mountaintops and deserts, and their important place in folklore and the arts. She explains tree fundamentals and considers the symbolic role they have assumed in culture and religion. In a book that reawakens our sense of wonder at the fascinating world of trees, we ultimately find entry to the entire natural world and rediscover our own place in it.
Evidence is mounting that global warming enhances a cyclone's damaging winds and flooding rains
An evolutionary interpretation of succession includes the following points. First, in order for a population to be well adapted to a particular set of conditions, it cannot be adapted to many different sets. There is an apparent limit to the width of niche and of habitat that a population can exploit effectively. Selection preserves these unique adaptations and fosters population coupling with the environment. Second, succession provides a complex gradient of physical and biotic environments, analogous to spatial gradients, to which species respond in both ecological and evolutionary time. Selection adjusts the positions of populations on successional gradients in the same way they are adjusted on spatial gradients. Third, the evolutionary strategy, which involves life-cycle length, time of reproduction, reproductive output, and ultimately the degree of recombination, is a basic determinant of species position on both spatial and successional gradients. Fourth, patches of different successional environmen...
[1] Recent studies have shown that there has been a reduction in dry season moisture input from direct interception of cloud water and wind-blown mist at the lee edge of the Monteverde cloud forest, Costa Rica, since the mid 1970s. This reduction of moisture could be responsible for the population crashes of anurans observed in the region. It has been hypothesized that this behavior is a result of increases in cloud base height, linked to increased sea surface temperatures. In this study we present a complementary hypothesis, that deforestation upwind of the Monteverde cloud forest preserve is responsible for the observed changes in cloud base height. An automated cumulus cloud classification scheme extracts monthly spatial maps of the frequency of occurrence of cumulus cloudiness over Costa Rica from GOES 8 visible channel satellite imagery. We find that cumulus cloud formation in the morning hours over deforested regions is suppressed compared to forested areas. The degree of suppression appears to be related to the extent of deforestation. This difference in cloud formation between forested and deforested areas is a clear signal of land use change influencing the regional climate. Regional Atmospheric Modeling System numerical modeling simulations are used to explore the differences in cloud field characteristics over the lowland pasture and forest landscapes. Statistically significant differences in cloud base height and cloud thickness occur between the forest and pasture simulations. Clouds have higher base heights and are thinner over pasture landscapes than over forested ones. On the other hand, these simulations show no statistically significant differences in cloud top heights, cloud cover, mean cloud water mixing ratio, or cloud liquid water path between pasture and forest simulations. However, in the simulations there are enhanced sensible heat fluxes and reduced latent heat fluxes over pasture compared to forest. It is the drier and warmer air over pasture surfaces that results in the formation of elevated thinner clouds. This study suggests that deforestation results in warmer, drier air upwind of the Monteverde cloud forests and that this could influence the base height of orographic cloudbanks crucial to the region during the dry season.
Startling amounts of ice slipping into the sea have taken glaciologists by surprise; now they fear that this century's greenhouse
emissions could be committing the world to a catastrophic sea-level rise, as detailed in series of reports in this issue (see
www.sciencemag.org/sciext/ice). (Read more.)
Demographic structure of 12 chaparral sites unburned for 56 to 120 years was investigated. All sites were dominated by vigorous shrub populations and, although there was colonization by seedlings of woodland tree species in several stands, successional replacement of chaparral was not imminent. Although successional changes in community composition were evident, there was no indication of a decline in species diversity. Non-sprouting species of Ceanothus suffered the greatest mortality at most, but not all, sites. Sprouting shrubs, such as Quercus and Heteromeles had very little mortality, even in stands more than a century old. All postfire resprouting species had multiple stems of different ages indicating these shrubs were capable of continuously regenerating their canopy from basal sprouts. Ceanothus populations were highly clumped and there was a significant correlation across all sites between variance/mean ratio and percentage mortality. As Ceanothus populations thinned, they became less clumped. In mixed chaparral stands, Quercus and Heteromeles were significantly taller than associated Ceanothus shrubs and overtopped the Ceanothus; at two sites, the density of live Quercus per plot was correlated with the density of dead Ceanothus. Thus, mortality of Ceanothus stems is likely related to both intra and interspecific interations.
Tsuga canadensis is the dominant in four topo-edaphic associations and one edaphic association in Ohio. WhileTsuga may occur withPinus strobus and a variety of deciduous trees (e.g.,Fagus grandifolia, Acer saccharum) in these communities, only hemlock is persistently reproducing. As compared with the contiguous mesophytic deciduous forest, these associations have a depauperate understory, a possible consequence of the shallow and generally coarse soils and low light intensity in these habitat types. The narrow gorge microhabitat of theT. canadensis-Dryopteris intermedia habitat type and the northerly exposure of theT. canadensis-D. marginales habitat type with lower light intensity and lower evapotranspiration allow the establishment and maintenance of hemlock to the exclusion of most deciduous tree species. In addition, the gorges provide some fire protection, and due to their general inaccessibility, protection from logging. These Ohio hemlock associations bear little floristic similarity to the more extensive climatic climax hemlock communities in southern Ontario, possibly reflecting elimination of most boreal associates in Ohio with climatic change since the end of the Pleistocene.
Comparisons of population genetic diversity between related rare and widespread species provide valuable insights to the consequences of rarity and are critical for conservation planning. Population genetic diversity of A. maritima, a rare species, was compared with its common, widespread congener A. serrulata to evaluate the impacts of small population size and high isolation on genetic diversity in A. maritima and to provide population genetic data to be used in conservation planning for A. maritima. Genetic data were also used to evaluate whether the disjunct distribution of A. maritima was due to range reduction or anthropogenic dispersal. Genetic diversity was lower in A. maritima (H(e) = 0.217) than in A. serrulata (H(e) = 0.268), and there is also higher inbreeding within A. maritima populations (f = 0.483) than A. serrulata populations (f = 0.269). The partitioning of genetic variation was also higher among A. maritima populations (Θ = 0.278), but not significantly different from that of A. serrulata (Θ = 0.197). Significant genetic differences among A. maritima populations support using local populations as seed sources for regional conservation efforts. The results also indicate that the highly disjunct distribution of A. maritima is due to natural range reduction in the past and not anthropogenic establishment of Oklahoma and Georgia populations.
The announcement this week of a bacterium that appears to derive energy from light despite living in the inky depths of an
ocean threatens to overthrow the dogma that photosynthesis depends on the sun.
Ecology has expanded from its traditional focus on organisms to include studies of the Earth as an integrated ecosystem. Aided by satellite technologies and computer models of the climate of the Earth, global change ecology now records basic parameters of our planet, including its net primary productivity, biogeochemical cycling and effects of humans on it. As I discuss here, this new perspective shows us what must be done to transform human behaviors to enable the persistence of life on Earth under human stewardship.
LONGYEARBYEN, NORWAY--
The prime ministers of five Nordic countries gathered here on the arctic archipelago of Svalbard last week to mark the beginning
of a unique bunker: an underground vault that will hold up to 3 million seeds. (Read more.)
CLIMATE CHANGE Four climate scientists at the National Oceanic and Atmospheric Administration calculate that the greenhouse was behind more than half of last yeari?½s record-breaking warmth across the contiguous United States.
New information about Easter Island is helping to identify the cause of the massive deforestation that occurred prior to European
arrival, but unanswered questions remain.
Having issued their fair and balanced consensus document, many climate scientists now cite oft-overlooked reasons for immediate
and forceful action to curb global warming.
Abundant liquid water newly discovered underneath the world’s great ice sheets could intensify the destabilizing effects of global warming on the sheets. Then, even without melting, the sheets may slide into the sea and raise sea level catastrophically