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Rate of tree carbon accumulation increases continuously with tree size
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Forests are major components of the global carbon cycle, providing
substantial feedback to atmospheric greenhouse gas concentrations1
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Our ability to understand and predict changes in the forest carbon
cycle—particularly net primary productivity and carbon storage—
increasingly relies on models that represent biological processes
across several scales of biological organization, from tree leaves to
forest stands2,3. Yet, despite advances in our understanding of productivity
at the scales of leaves and stands, no consensus exists about
the nature of productivity at the scale of the individual tree4–7, in
part because we lack a broad empirical assessment of whether rates
of absolute treemass growth (and thus carbon accumulation) decrease,
remain constant, or increase as trees increase in size and age. Here we
present a global analysis of 403 tropical and temperate tree species,
showing that for most species mass growth rate increases continuously
with tree size. Thus, large, old trees do not act simply as senescent
carbon reservoirs but actively fix large amounts of carbon
compared to smaller trees; at the extreme, a single big tree can add
the same amount of carbon to the forest within a year as is contained
in an entire mid-sized tree. The apparent paradoxes of individual
tree growth increasing with tree size despite declining leaf-level8–10
and stand-level10 productivity can be explained, respectively, by
increases in a tree’s total leaf area that outpace declines in productivity
per unit of leaf area and, among other factors, age-related
reductions in population density. Our results resolve conflicting
assumptions about the nature of tree growth,inform efforts to undertand
and model forest carbon dynamics, and have additional implications
for theories of resource allocation11 and plant senescence1
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Risk Communication on Climate: Mental Models and Mass Balance
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Public confusion about the urgency of reductions
in greenhouse gas emissions results from a basic
misconception.
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When the river runs dry: human and ecological values of dry riverbeds
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Temporary rivers and streams that naturally cease to flow and dry up can be found on every continent.
Many other water courses that were once perennial now also have temporary flow regimes due to the effects
of water extraction for human use or as a result of changes in land use and climate. The dry beds of these
temporary rivers are an integral part of river landscapes. We discuss their importance in human culture and
their unique diversity of aquatic, amphibious, and terrestrial biota. We also describe their role as seed and
egg banks for aquatic biota, as dispersal corridors and temporal ecotones linking wet and dry phases, and as
sites for the storage and processing of organic matter and nutrients. In light of these valuable functions, dry
riverbeds need to be fully integrated into river management policies and monitoring programs. We also
identify key knowledge gaps and suggest research questions concerning the values of dry riverbeds.
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The energetic implications of curtailing versus storing solar- and wind-generated electricity
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We present a theoretical framework to calculate how storage affects the energy return on energy
investment (EROI) ratios of wind and solar resources. Our methods identify conditions under which it is
more energetically favorable to store energy than it is to simply curtail electricity production.
Electrochemically based storage technologies result in much smaller EROI ratios than large-scale
geologically based storage technologies like compressed air energy storage (CAES) and pumped
hydroelectric storage (PHS). All storage technologies paired with solar photovoltaic (PV) generation yield
EROI ratios that are greater than curtailment. Due to their low energy stored on electrical energy
invested (ESOIe) ratios, conventional battery technologies reduce the EROI ratios of wind generation
below curtailment EROI ratios. To yield a greater net energy return than curtailment, battery storage
technologies paired with wind generation need an ESOIe > 80. We identify improvements in cycle life as
the most feasible way to increase battery ESOIe. Depending upon the battery's embodied energy
requirement, an increase of cycle life to 10 000–18 000 (2–20 times present values) is required for
pairing with wind (assuming liberal round-trip efficiency [90%] and liberal depth-of-discharge [80%]
values). Reducing embodied energy costs, increasing efficiency and increasing depth of discharge will
also further improve the energetic performance of batteries. While this paper focuses on only one
benefit of energy storage, the value of not curtailing electricity generation during periods of excess
production, similar analyses could be used to draw conclusions about other benefits as well
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Ecologists Report Huge Storm Losses in China’s Forests
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From delicate orchids and magnolias to rare Chinese yews and Kwangtung pines, the flora of Guangdong
Nanling National Nature Reserve is considered so precious that ecologists call the reserve “a treasure trove of species.” But winter storms have reduced the biological hot spot to a splintered ruin. Snow, sleet, and ice laid waste to 90% of the 58,000- hectare reserve’s forests, says He Kejun, director of Guangdong Forestry
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Challenges in the conservation, rehabilitation and recovery of native stream salmonid populations: beyond the 2010 Luarca symposium
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– In May 2010, I chaired a session on challenges to salmonid conservation at the international symposium
‘Advances in the population ecology of stream salmonids’ in Luarca, Spain. I suggested that in addition to scientific challenges, a major challenge will be improving the links between ecologists, conservationists and policy makers. Because the Luarca symposium focused mainly on ecological research, little time was explicitly devoted to conservation. My objective in this paper is to further discuss the role of ecological research in informing salmonid conservation. I begin with a brief overview of research highlights from the symposium. I then use selected examples to show that ecological research has already contributed much towards informing salmonid conservation, but that ecologists will always be faced with limitations in their predictive ability. I suggest that conservation will need to move forward regardless of these limitations, and I call attention to some recent efforts wherein ecological research has played a crucial role. I conclude that ecologists should take urgent action to ensure that their results are availableto inform resource managers, conservation organisations and policy makers regarding past losses and present threats to native, locally-adapted salmonid stocks.
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Climate change impacts on the biophysics and economics of world fisheries
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Global marine fisheries are underperforming economically because of overfishing, pollution and habitat degradation. Added to these threats is the looming challenge of climate change. Observations, experiments and simulation models show that climate change would result in changes in primary productivity, shifts in distribution and changes in the potential yield of exploited marine species, resulting in impacts on the economics of fisheries worldwide. Despite the gaps in understanding climate change effects on fisheries, there is sufficient scientific information that highlights the need to implement climate change mitigation
and adaptation policies to minimize impacts on fisheries.
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Dissecting insect responses to climate warming: overwintering and post-diapause performance in the southern green stink bug, Nezara viridula, under simulated climate-change conditions
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The effect of simulated climate change on overwintering and postdiapause
reproductive performance is studied in Nezara viridula (L.) (Heteroptera:
Pentatomidae) close to the species’ northern range limit in Japan. Insects are reared
from October to June under quasi-natural (i.e. ambient outdoor) conditions and in
a transparent incubator, in which climate warming is simulated by adding 2.5 ◦
C to
the ambient temperatures. Despite the earlier assumption that females of N. viridula
overwinter in diapause, whereas males do so in quiescence, regular dissections show
that the two sexes overwinter in a state of true diapause. During winter, both sexes are
dark-coloured and have undeveloped reproductive organs. Resumption of development
does not start until late March. During winter, the effect of simulated warming on the
dynamics and timing of physiological processes appears to be limited. However, the
warming significantly enhances winter survival (from 27–31% to 47–70%), which
is a key factor in range expansion of N. viridula. In spring, the effect of simulated
warming is complex. It advances the post-diapause colour change and transition from
dormancy to reproduction. The earlier resumption of development is more pronounced
in females: in April, significantly more females are already in a reproductive state
under the simulated warming than under quasi-natural conditions. In males, the
tendency is similar, although the difference is not significant. Warming significantly
enhances spring survival and percentage of copulating adults, although not the percentage
of ovipositing females and fecundity. The results suggest that, under the expected
climate-warming conditions, N. viridula will likely benefit mostly as a result of
increased winter and spring survival and advanced post-diapause reproduction. Further
warming is likely to allow more adults to survive the critical cold season and contribute
(both numerically and by increasing heterogeneity) to the post-overwintering population
growth, thus promoting the establishment of this species in newly-colonized
area
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The Holocene`
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Combining nine tree growth proxies from four sites, from the west coast of Norway to the Kola Peninsula of NW Russia, provides a well replicated
(> 100 annual measurements per year) mean index of tree growth over the last 1200 years that represents the growth of much of the northern pine
timberline forests of northern Fennoscandia. The simple mean of the nine series, z-scored over their common period, correlates strongly with mean
June to August temperature averaged over this region (r = 0.81), allowing reconstructions of summer temperature based on regression and variance
scaling. The reconstructions correlate significantly with gridded summer temperatures across the whole of Fennoscandia, extending north across Svalbard
and south into Denmark. Uncertainty in the reconstructions is estimated by combining the uncertainty in mean tree growth with the uncertainty in
the regression models. Over the last seven centuries the uncertainty is < 4.5% higher than in the 20th century, and reaches a maximum of 12% above
recent levels during the 10th century. The results suggest that the 20th century was the warmest of the last 1200 years, but that it was not significantly
different from the 11th century. The coldest century was the 17th. The impact of volcanic eruptions is clear, and a delayed recovery from pairs or multiple
eruptions suggests the presence of some positive feedback mechanism. There is no clear and consistent link between northern Fennoscandian summer
temperatures and solar forcing.
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The Wheel of Life Food, Climate, Human Rights, and the Economy
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The links between climate change and industrial agriculture create a nexus of crises—food
insecurity, natural resource depletion and degradation, as well as human
rights violations and inequities.
While it is widely recognized that greenhouse gas (GHG) emissions due
to human activity are detrimental to the natural environment, it can be difficult to
untangle the cascading effects on other sectors. To unravel some of the effects, this
paper focuses on three interrelated issues:
1) What are the critical links between climate change and agriculture?
2) How is the nexus of agriculture and climate change affecting human societies
particularly regarding food and water, livelihoods, migration, gender
equality, and other basic survival and human rights?
3) What is the interplay between economic and finance systems, on the one
hand, and food security, climate change, and fundamental human rights, on
the other?
In the process of drawing connections among these issues, the report will identify
the commonality of drivers, or “push” factors, that lead to adverse impacts.
A central theme throughout this report is that policies and practices must
begin with the ecological imperative in order to ensure authentic security and stability
on all fronts including food, water, livelihoods and jobs, climate, energy, and
economic. In turn this engenders equity, social justice, and diverse cultures. This
imperative, or ethos of nature, is a foundation that serves as a steady guide when
reviewing mitigation and adaptation solutions to climate change.
Infused within this theme is the sobering recognition that current consumption
and production patterns are at odds with goals of reducing GHGs and attaining
global food security. For instance, consumption and production levels, based on the
global average, are 25 percent higher than the earth’s ecological capacity.1
As societies
address the myriad ecological and social issues at the axis of global warming,
a central task will be to re-align consumption and production trends in a manner
that can fulfill economic and development requirements. This will require a major
shift away from present economic growth paradigms based on massive resource
extraction and toward creating prosperous and vital societies and economies that
preserve the planet’s environmental capacity
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