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Assemblage Time Series Reveal Biodiversity Change but Not Systematic Loss
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The extent to which biodiversity change in local assemblages contributes to global biodiversity
loss is poorly understood. We analyzed 100 time series from biomes across Earth to ask how diversity
within assemblages is changing through time. We quantified patterns of temporal a diversity, measured
as change in local diversity, and temporal b diversity, measured as change in community composition.
Contrary to our expectations, we did not detect systematic loss of a diversity. However, community
composition changed systematically through time, in excess of predictions from null models.
Heterogeneous rates of environmental change, species range shifts associated with climate change,
and biotic homogenization may explain the different patterns of temporal a and b diversity.
Monitoring and understanding change in species composition should be a conservation priority.
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From Past to Future Warming
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Analyses of past observations help to
predict the human contribution to future
climate change.
21 FEBRUARY 2014 VOL 343 SCIENCE
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Carbon Market Lessons and Global Policy Outlook
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Summary: Ongoing work on linking markets and mixing policies builds on successes and failures in pricing and trading carbon. Closing sentence, 1st paragraph: Are carbon markets seriously challenged or succeeding and on the rise?
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Status and Ecological Effects of the World’s Largest Carnivores
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The largest terrestrial species in the order Carnivora are wide-ranging and rare
because of their positions at the top of food webs. They are some of the world’s most admired mammals
and, ironically, some of the most imperiled. Most have experienced substantial population
declines and range contractions throughout the world during the past two centuries. Because of the
high metabolic demands that come with endothermy and large body size, these carnivores often
require large prey and expansive habitats. These food requirements and wide-ranging behavior
often bring them into confl ict with humans and livestock. This, in addition to human intolerance,
renders them vulnerable to extinction. Large carnivores face enormous threats that have caused
massive declines in their populations and geographic ranges, including habitat loss and degradation,
persecution, utilization, and depletion of prey. We highlight how these threats can affect the
conservation status and ecological roles of this planet’s 31 largest carnivores.
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Coupling of CO2 and Ice Sheet Stability Over Major Climate Transitions of the Last 20 Million Years
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During the Middle Miocene, when temperatures were ~3° to 6°C warmer and sea level 25 to 40 meters higher than present, pCO2 was similar to modern levels.
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Changes in Wind Pattern Alter Albatross Distribution and Life-History Traits
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Westerly winds in the Southern Ocean have increased in intensity and moved poleward. Using
long-term demographic and foraging records, we show that foraging range in wandering albatrosses
has shifted poleward in conjunction with these changes in wind pattern, while their rates of travel and
flight speeds have increased. Consequently, the duration of foraging trips has decreased, breeding
success has improved, and birds have increased in mass by more than 1 kilogram. These positive
consequences of climate change may be temporary if patterns of wind in the southern westerlies
follow predicted climate change scenarios. This study stresses the importance of foraging performance
as the key link between environmental changes and population processes.
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Freshwater Methane Emissions Offset the Continental Carbon Sink
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Acornerstone of our understanding of the
contemporary global carbon cycle is that
the terrestrial land surface is an important
greenhouse gas (GHG) sink (1, 2). The global
land sink is estimated to be 2.6 T 1.7 Pg of C
year−1 (variability T range, excluding C emissions
because of deforestation) (1). Lakes, impoundments,
and rivers are parts of the terrestrial landscape,
but they have not yet been included in the
terrestrial GHG balance (3, 4). Available data
suggest, however, that freshwaters can be substantial
sources of CO2 (3, 5) and CH4 (6). Over time,
soil carbon reaches freshwaters by lateral hydrological
transport, where it can meet several fates,
including burial in sediments, further transport to
the sea, or evasion to the atmosphere as CO2 or
CH4 (7). CH4 emissions may be small in terms of
carbon, but CH4 is a more potent GHG than CO2
over century time scales. This study indicates that
global CH4 emissions expressed as CO2 equivalents
correspond to at least 25% of the estimated
terrestrial GHG sink.
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Not All About Consumption
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Resource exploitation can lead to increased
ecological impacts even when overall
consumption levels stay the same
15 March 2013 VOL 339 SCIENCE
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Defaunation in the Anthropocene
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We live amid a global wave of anthropogenically driven biodiversity loss: species
and population extirpations and, critically, declines in local species abundance.
Particularly, human impacts on animal biodiversity are an under-recognized form of
global environmental change. Among terrestrial vertebrates, 322 species have
become extinct since 1500, and populations of the remaining species show 25%
average decline in abundance. Invertebrate patterns are equally dire: 67% of
monitored populations show 45% mean abundance decline. Such animal declines
will cascade onto ecosystem functioning and human well-being. Much remains unknown
about this “Anthropocene defaunation”; these knowledge gaps hinder our capacity
to predict and limit defaunation impacts. Clearly, however, defaunation is both a
pervasive component of the planet’s sixth mass extinction and also a major driver of
global ecological change
25 JULY 2014 • VOL 345 ISSUE 6195
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How Does Climate Change Affect Biodiversity?
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The most recent and complex bioclimate
models excel at describing species’ current
distributions. Yet, it is unclear which models
will best predict how climate change will affect
their future distributions.
8 SEPTEMBER 2006 VOL 313 SCIENCE
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