[permaculture] what are your thoughts... Re: BBC NEWS | Science/Nature | Warming world sends plants uphill
jordan at riseup.net
jordan at riseup.net
Fri Jun 27 22:07:49 EDT 2008
I've been getting into geological history, astrobiology, et c. to inform
my permaculture teaching...
this study seems contradictory to what the history of life would indicate
for example, the last 30 million years (including the current period) has
lowest temperatures and lowest CO2 levels since 150 million years ago...
we are in a long-ice age and each glacial period since the beginning of
this ice age has been colder than the next... yeah we've extended this
interglacial for the last 5000 years (it's beinning to look like the even
temps of the last several thousand years are a result of agriculture
releasing methane and carbon dioxide) and industry has pushed it a little
higher than interglacial go, but we are not like most of the earths
history where it has been warm.
It may be counter-intuitive, but warm periods in earth's history (such as
the Eocene) we very very wed. during the eocene, it was aboutt he same at
the equator, tropical to 45º and temperate to the poles (dawn redwoods
grew on island near the poles. the whole planet was forested, not desert
or grassland... because the warm air could hold so much water and there
was so much evaporation from oceans... it was wet.
it wasn't until the arctice ocean was sealed off from the rest of the
oceans by north american plate that things started to change. the arctic
had no current and so it formed an oxygen free layer underneath a top
layer of freshwater from streams. Imagine a warm, freshwater, temperate
ocean that 20-hour days in the northern summer... azolla, the n-fixing
water-fern took over the ocean and, when it would die, would sink into the
anerobic bottom and get trapped from decomposing...
over 800,000 years this took 80% of the world's CO2 out of the atmosphere
and started the cooling that lead to our current ice-age.
grasslands and deserts happened because of this cooling... with less temp,
the air held less moisture. with the overall decrease in CO2, C4 plants,
like grasses which can live on less CO2 were well-adapted.
so here is my question... why would global warming lead to increased
desertification and a benefit to grasses. in my bioregion Douglas firs
have evidence in the fossil record 50 million years, to the triassic and
confirmed fossils are found in navada in the eocene... which was warm and
wet and tropical...
I guess i don't see how warming will do what this article says...
> Page last updated at 13:37 GMT, Friday, 27 June 2008 14:37 UK
> Warming world sends plants uphill
> French mountains (Image: Science)
> Trees and shrubs are likely to be most threatened by rising temperatures
> Climate change has caused plants to seek cooler conditions at higher
> altitudes, scientists suggest.
> A study of 171 forest species in mountain ranges of western Europe found
> that many plants had climbed an average of 29
> metres each decade.
> Smaller species such as ferns, which had shorter reproduction cycles, were
> the quickest to relocate, the researchers said.
> The findings have been published in the Science journal.
> "This is the first time that it has been shown that climate change has
> already had a significant effect on plant species
> over a wide range of temperatures during the past century," explained
> Jonathan Lenoir, the paper's lead author.
> Climate 'fingerprints'
> Professor Lenoir, an ecologist at AgroParisTech, France, said the team
> wanted to establish whether "fingerprints of
> climate change were already apparent in ordinary ecosystems".
> In order to do this, the team of French and Chilean researchers compared
> the distribution of forest species between 1905
> and 1985 with their distribution between 1986 and 2005.
> "This work was possible because of two large-scale, long-term databases
> that have recorded the presence of forest
> species since 1905," he explained.
> This may imply profound changes in the composition and structure of plant
> communities and animal species that depend
> upon them
> Professor Jean-Claude Gegout,
> "We used 171 species commonly found over French mountains, which are part
> of Mediterranean, temperature and mountainous
> forest ecosystems between 0m to 2,600m above sea level.
> "We found a significant change in species' altitudinal distribution
> towards higher elevation of about 29 metres per decade.
> "Out of the 171 species, most are shifting upwards to recover temperature
> conditions that are optimal for their
> development and reproduction."
> Co-author Jean-Claude Gegout added that different types of plants
> displayed different responses to the temperature changes.
> "Long-life plants, such as trees and shrubs, did not show significant
> shifts, whereas short-life species, such as herbs,
> showed a strong upward shift," he said.
> "Herbs, by having a short life cycle, have had several generations during
> a decade that allows for a faster dispersal of
> "By contrast, trees have had just one or two generations during the same
> period of time, which may affect their ability
> to track the climate changes."
> Professor Gegout said that this suggested that long living woody plant
> species, such as trees, were likely to be more
> threatened by climate change than herb species like grasses.
> "This may imply profound changes in the composition and structure of plant
> communities and animal species that depend
> upon them."
> The researchers concluded by saying that further studies were needed to
> understand the full magnitude of the changes,
> and to assess the impact on the ecosystems' long-term future.
> SEE ALSO
> The slippery slope of winter sports
> 06 Aug 07 | Science/Nature
> Snow sports 'stress' to wildlife
> 07 Mar 07 | Science/Nature
> New 'lookouts' for climate change
> 18 Jun 08 | Highlands and Islands
> Extinction fear for butterflies
> 13 May 08 | Highlands and Islands
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