Hello Tom and Byron,
The building of all these hydro dams doesn't help either. Belo Monte
being one of the biggest in Brazil currently altering the entire river
ecosystem in its immediate region.
Also the deforestation has been found to impact localised weather
patterns and to break up the cloud formations that create that
rainforest weather. This happens even when the break in canopy cover is
as little as (I think it was?) 50 metres wide. The paper which discussed
this was something I read a couple of years ago but I cannot recall the
title. Will have look for it. It has something to do with atmospheric
humidity directly above the tree canopy. If it is incomplete then the
flow of humid air stop short of the next section of rainforest at the
edge of the gap and because there is no or very little vegetation in the
gap the humidity disappears and in time the part it cannot reach then
dies due to lack of rainfall. It may be as wet as hell elsewhere but the
places separated by breaks in the canopy will suffer. The fragmentation
of habitats is a big issue not just for rainforests though. We have
issues here in the UK with our ordinary woodlands.
Kev C
On 13/07/2012 16:05, Barker, Tom wrote:
> The Amazon will be a major drought zone if the Hadley projections are correct. They show that the forest has had it unfortunately. Tom
>
> ________________________________________
> From: Discussion list for the Crisis Forum [[log in to unmask]] on behalf of Byron Smith [[log in to unmask]]
> Sent: 13 July 2012 15:52
> To: [log in to unmask]
> Subject: Re: Tropical forests spreading?
>
> Greetings all,
>
> If I may return to the Nature paper by Higgins & Scheiter [1] that Prof Northcott posted a couple of days ago, having now had a chance to read it, I note the following in the penultimate main paragraph:
>
> "Although these projections of increasing tree dominance seem to contradict studies that project forest dieback in the Amazon, this may simply be because our analysis assumes that rainfall remains constant, whereas projections of Amazon forest dieback are based on climate simulations that project decreased rainfall. The high uncertainty in precipitation change over Africa led us to assume that rainfall remained at ambient levels (see Supplementary Information), but future studies should consider changes in rainfall as well as feedbacks between vegetation and rainfall."
>
> So while CO2 trumps temperature in shifting ecosystems from C4 to C3 dominated flora (i.e. savanna/grasslands to forest), hydrological changes could well trump them both, as is generally thought to be most likely for much of Amazonia. Rhett Butler (Mongabay.com), a leading environmental journalists, sought feedback on the paper from a number of Amazon experts concerning the applicability of extending this analysis to South America and found strong reservations across the board.[2] The hydrological projections for Africa that I've seen are indeed mixed, but more recent ones seem to point to some significantly lower levels of precipitation for southern Africa in particular.[3]
>
> And both the opening and final paragraph of the Higgins & Scheiter piece note that land use changes are a further wildcard.
>
> So, yes, acknowledging the complexity of global change trajectories involves honesty about possible negative feedbacks slowing rates of change, as well as appreciating the resilience and adaptability of both natural and human systems. And invoking apocalyptic language and imagery in the discussion of ecological crises confuses both the relevant science and (I would argue) theology. On all this I agree with Michael. But this particular study has some fairly major caveats to observe before it might give us too much hope of a soft landing.
>
> We're not out of the woods (or rather, back into them) yet.
>
> [1] http://www.nature.com/nature/journal/vaop/ncurrent/full/nature11238.html
> [2] http://news.mongabay.com/2012/0712-telegraph-poor-science-journalism.html
> [3] For example: http://journals.ametsoc.org/doi/pdf/10.1175/2009JCLI2317.1.
>
> Regards,
> Byron Smith
>
> PhD candidate
> University of Edinburgh
--
"Wisdom is what's left after we've run out of personal opinions." Cullen
Hightower
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