on the Ground
Resources: Now and for the Future
363 000 people were born
154 000 died
World population increased by 209 000
Annual world population increase:
2008 77 M, 2009 80 M, 2010 78 M, 2011 76
degradation: startling new results
The Global Assessment
of Land Degradation (GLADA)
A Global Assessment of Land
Degradation, monitored from satellite imagery over a 22-year period,
has recently been made. The results are unexpected -- to say the
least! They cast doubt on widely-held assumptions about where
soil and land degradation.
For nearly 30 years, the
world has been dependent on the Global Assessment of Soil Degradation
(GLASOD). This was an attempt to estimate the state of degradation
in about 1990, resulting from the cumulative effects throughout
the history of land use. It was based on subjective assessment,
estimates by soil scientists who knew conditions in their countries.
GLADA differs in two respects.
First, it measures recent trends in degradation, over the period
1981-2003. Secondly, it is based on an objective method, monitoring
the Normalized Difference Vegetation Index (NDVI) obtained annually
from satellite data, based on an 8 km grid. NDVI is well-established
as a way of estimating net primary production by plants (NPP),
or plant growth. The main climatic variables are allowed for by
correcting the data for rainfall and temperature. Changes in land
use could not be allowed for, because there is no time-series
of data. Where adjusted NPP has fallen, this is assumed to be
due to adverse soil changes, land degradatiton. Where it has increased,
it results from land improvement.
For GLADA results see the
Report, an account on the
FAO LADA site, and a guide to country studies on the ISRIC
Results: where is degradation
GLASOD estimated degraded
land, cumulative over the entire history of land use. GLADA measures
degrading land, trends over the period 1981-2003. These
two sets of results would not be expected to follow the same pattern.
Even so, the results are highly unexpected.
Where is it widely believed
that the state of the land is really bad? The Sahel (semi-arid)
belt of Africa is one such area, where degradation is commonly
referred to by the widely misused term 'desertification'. Another
area is the Amazon rain forest, where widespread forest clearance
is certainly taking place. More generally, it was supposed that
drylands are the worst affected. Indeed, the present study was
commissioned as part of the LADA project, Land Degradation in
Drylands; the humid regions were included for comparison.
But the African Sahel and
the Amazon rain forest largely show land improvement, an increase
in climate-adjusted plant growth. So do most of the world's drylands.
78% of the currently-degrading land is in the humid regions --
not a finding expected by a study directed at drylands!
The most severely
degrading areas are:
- The Central African
(Congo) forest, and savanna areas to the east and south of it,
including Transvaal and Natal in South Africa.
- South East Asia, both
mainland and insular, including Indo-China, Malaysia and Indonesia,
together with South China.
Other regions where plant
growth has decreased include much of Mexico, the Argentinian Pampas,
the high-latitude forest belt of Canada, and parts of the Great
Dividing Range of Australia. As GLADA puts it, "the usual
suspects", such as around the African Sahel, the Mediterranean
and the Middle East, are only lightly affected. Most of India
appears to have recent land improvement, although Bangladesh and
Nepal show degradation.
The worst affected countries,
with >50% of their territory degrading, are, in Africa the
Congo, Zaire, Equatorial Guinea, Gabon, Sierra Leone, Zambia,
and the most affected (95% degrading) Swaziland; in Asia, Myanmar,
Malaysia, Thailand, Laos, Korea (N and S), and Indonesia; plus
a surprise, New Zealand.
Pundits will want to debate
the validity of these findings. As they stand, they challenge
current notions and open up debate. The scientific cat is among
the pigeons of long-held assumptions.
The authors of this study
themselves pose the question, "Is the biomass trend indicated
by GLADA real?", but do not attempt to answer this. They
expect to set up a GLADA web site for discussion.
Another surprise: is
rising atmospheric carbon dioxide increasing world plant growth?
There is another unexpected,
and unintended, finding. Over the 22-year period, world plant
growth has increased by 3.8%. Graphs of annual data show fluctuations
with 2-5 year periods, but a steady upward trend. This trend is
found for all six continents.
The authors of GLADA note
this result, but refrain from commenting upon it. but there is
an intriguing possibility. Could the rise in atmospheric carbon
dioxide (CO2) be
leading to faster plant growth? Plants grow by photosynthesis,
taking up carbon dioxide and giving out oxygen. The benefits of
adding supplementary CO2 to horticultural
greenhouses are well known. A steady rise in CO2
has taken place over the period of the study.
Could we be witnessing a
'greenhouse effect' - in a different sense! - on a world scale?
If this were the case, there might be the makings of a global
self-adjusting mechanism, taking more CO2
out of the atmosphere. It could well be that we are not seeing
this damping mechanism because at present it is swamped by rising