THE
SPIRIT OF PLANTS - CLOUDS
A
long time ago, in the last century (at the beginning of the 90's), I had the
opportunity to make a trip to Cyprus, a beautiful Mediterranean island with a
particularly rich historical past. I was struck by the incredible amount of
forest tree replanting in all non-agricultural areas, especially mountain
areas, sometimes terraced.
I
was then told that it was a government plan to stop the evolution of the local
climate. Rains were becoming increasingly rare, and the island was slowly
moving towards a significant risk of desertification.
We
empirically know, and for a long time, that forests promote the appearance of
rains, to the point that certain countries with an arid climate, as it's the
case of Cyprus, have launched reforestation programs, sometimes very ambitious,
of which one the main objectives are to try to increase rainfall, in addition
to curbing erosion and loss of soil fertility.
What
we now know, thanks to the Cloud experiment, a series of scientific works
conducted by the CERN, in Geneva, Switzerland, is how this phenomenon occurs.
I
advise you to read the original article (in French), full of interesting links
and explanations.
"Climate: According to the CERN, trees influence cloud formation.
As the
results of the Cloud experiment at CERN showed in 2016, the trees would be much
talented than we thought to make clouds and cool the climate. Their action goes
through aerosols.
Since 2009, the Cloud experiment,
installed at the CERN in Geneva, simulates different pressure and temperature
conditions to study mechanisms at work in the Earth's atmosphere, including the
effect of aerosols on the climate. These small particles act like "cloud
seeds", favoring the condensation of water vapor into droplets and thus
the formation of nebulosities. Overall, the effect on the climate is refreshing
because part of the sunlight is then reflected upwards.
Half of these aerosols are dust
from soils and marine salts emitted by the ocean, and the other half from gas
molecules that aggregate into particles of 50 to 100 nanometers. This is the
case of sulfuric acid, derived from sulfur dioxide (SO2). Today, this gas is
produced with great generosity by industrial activities. These aerosols of
human origin, creating more clouds, have a cooling effect, which reduces the
warming effect of carbon dioxide (CO2). It's a radiative forcing. Trees are
also actors in this machinery, with molecules, such as pinene, released into
the air, which also play the role of condensation nuclei.
The current amounts of sulfur
dioxide emissions complicate the study of the pre-industrial atmosphere, which
was different. This is what a Cloud team did, based on the results of this
experiment, to build a simulation of the pre-industrial atmosphere. Their
findings, published in the Pnas http://www.pnas.org/content/113/43/12053.abstract (and
discussed in an article in The Conversation https://theconversation.com/trees-are-much-better-at-creating-clouds-and-cooling-the-climate-than-we-thought-66713),
give more details on previous studies (…).
According to these results (still
uncertain, specify the authors), the quantities of aerosols present in the
Earth's atmosphere before 1750 have hitherto been underestimated, because the
aerosols emitted by trees are much more effective than thought to make clouds.
As a result, the cooling effect of industrial aerosols would be lower than
expected, by about 27%.
The authors also deduce that
limiting aerosol emissions by human activities could reduce their refreshing
action. But this decline could be offset by the action of trees, who are only
waiting to regain the importance they had in the pre-industrial era. In short,
forests are able to help us to limit global warming ... "
So,
given this very interesting experience, what about climate change in Cyprus?
I
found historical climate data on the World Bank web page http://sdwebx.worldbank.org/climateportal/
I
found two types of information, the accumulation of rain and the average
temperature, for the period 1901-2015. Here are the curves:
The
analysis of the curves shows us a clear tendency towards the increase of
temperatures, but a less clear tendency as regards rainfall. Because if the
rains tend to become more rare (the tendency line is clear), they are also much
more random. The years of insufficient rains are more frequent, but so are the
years of abundant rains. In short, with regard to rainfall, the average years
hardly exist anymore.
Obviously,
the effects of these reforestations are not clear. There, we can imagine many
possible reasons. Personally, I imagine that there is a great deal of
responsibility for the age of trees. They are roughly 25 years old (for those
who were planted in the 90's), and it's still very young. In addition, their
first years have probably not been easy, as in most reforestations in arid
regions, with difficulties of survival the first years for lack of rain during
the 3 or 4 summer months, and often numerous mortalities of young trees, to
which must probably be added parasitic attacks, such as certain insects fond of
stunted or precarious health plants.
In short,
without having seen them again, I'm sure they have a limited development. It's
clear that reforestation is a very long-term job, especially in arid regions.
Unless,
in fact, the fall in rainfall, proportionally lower than the increase in
temperature, is a sign of a good effect of these reforestations. In this case,
the desertification of Cyprus could have already progressed a lot, if this
program had not been launched sufficiently early.
That said,
and to return to aerosols, this very interesting work, will probably give rise
to further research, to study the production of these aerosols by age,
development, and especially by plant species. I imagine, as is the case for
many things in living beings, that there is an important variability of aerosol
production according to the plant species. One day, therefore, a list of
species more likely to fight desertification by the abundance of their aerosol
production will be developed.
Then humans
will face again a difficult ecological choice, like the one I told you in an
already old article, about the necessary freshwater savings and their
environmental consequences (http://culturagriculture.blogspot.com.es/2014/12/34-water-and-irrigation-3.html).
Shall we
massively plant species for their ability to promote rainfall even outside
their origin areas?
What
imbalances will we cause in the local biodiversity by the implantation of these
species?
Will
imbalances caused be preferable to desertification?
The eternal
problem of choice ... and its consequences.
While
waiting to have to make this choice, the GreenCyprusCom Foundation continues to
work for the reforestation of the island of Cyprus, with native species. It's
long, slow, laborious and expensive, but necessary.
Picture:
http://green-cyprus.com/upload/metadatas/1/1/soc_image/9115b612af06a52386bad740c6e508ea.jpg
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