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ISIS Special Miniseries - Why the United States Needs the Amazon

press-release

 

The Institute of Science in Society

Science Society Sustainability

http://www.i-sis.org.uk

 

General Enquiries sam

Website/Mailing List press-release

ISIS Director m.w.ho

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ISIS Special Miniseries

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Why the United States Needs the Amazon

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The ‘Tele’connection

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The US cornbelt will shrivel if the Amazon is destroyed. Peter Bunyard reports.

 

Diagrams and sources for this article are posted on ISIS Members’ website.

www.i-sis.org.uk\Membership.php

 

During the ‘Dust Bowl’ years of the 1930s, yields of wheat and maize plummeted

by 50 per cent as the soil just blew away in monstrous swirling clouds,

engulfing everything in their path. Hindsight tells us that much of the horrors

of those years resulted from putting the plough to wind-swept, vulnerable soils

that had never before been tilled. No hint of conservation practices then, not

like today. But just imagine how corn-belt farmers now would react to being told

that in the foreseeable future, a generation away at best, their sons and

daughters would be seeing their crops shrivel and die in the baking sun, the

precious soil once again blown away? And, we are not talking of a year once

every so often, but year after year in devastating succession, turning what was

the granary of the United States into desert.

 

 

So how come, given the difficulty we have of forecasting weather a few days’

hence, let alone days, months, or even years away, that we can come up with such

dire predictions? It all comes down to what is happening thousands of miles down

to the south, in the Amazon, to the way that the forest, covering nearly two

million square miles, pumps water that has fallen as rain back into the

atmosphere (see “Why Gaia needs rainforests”, this series).

 

 

As Brazilian physicists have shown, more than half the rain that falls over the

Amazon either gets evaporated from the tree trunks before it ever trickles to

the ground or gets pumped out as vapour through the millions upon millions of

pores found in every leaf. This combined process of evapo-transpiration puts

back into the atmosphere more than 6 million million tonnes of water vapour

every year - equivalent to staggering amounts of energy as the vapour condenses

into rain. And it is that energy - captured as masses of humid air – which

brings heat and rain to more temperate parts of the planet, and especially the

Americas. Argentina gets no less than half of its rain, courtesy of the Amazon.

The United States, too receives its share of the bounty.

 

 

Through an extraordinary process, recently unravelled by climatologists in the

United States, Brazil and Britain, we now know that what falls as rain over the

Amazon Basin is paralleled, three to four months later, in rain falling over the

US corn belt during its spring and summer. ‘Teleconnection’ is the name given to

the process that transfers energy and rain to the United States from Amazonia.

Relatively slow-moving moist masses of air, taking some months to complete their

journey, seek conduits in the atmospheric circulation system, pushing their way

through mass-circulation systems such as the Hadley Cell and the high flying

Easterlies. These waves of Amazonian air, fuelled by the water vapour they

carry, then release their rain en route over the corn-belt regions of the US.

 

 

We are talking of the rains that are essential for the growth and survival of

crops fundamental to the needs of the United States, let alone the rest of the

world. Let the forest wither away, or just cut it and burn it down, and the US

as well as the world will suffer like no-one had ever imagined they would.

 

 

The current US administration may have forgotten that in the drought of 1988,

caused by a powerful El Nino (see later), the United States had a foretaste of

what is to come. Corn yields fell by more than a quarter, swallowing up the

surpluses of previous years, and for the first time leaving production behind US

consumption. The federal government was forced to pay out three billion dollars

just in direct relief to farmers.

 

 

The irony is that much of the recent deforestation in the Brazilian Amazon,

particularly in the States of Mato Grosso and Para, is for growing soya beans to

meet the European demand for non-genetically modified produce, and in addition,

to feed China’s ever growing demands for soya-fed poultry and pigs. What we now

see, all too typically at Santarem in the State of Para, is none other than

thousands upon thousands of acres of monoculture soya, stretching from horizon

to horizon. The species-rich tropical forest has gone forever (see “Soya

destroying Amazon”, this series).

 

 

Climatologists at the UK Met Office’s Hadley Centre have already discovered

that, as the world warms up, the air currents bringing rain to the Amazon can

suddenly switch El Nino-like to a climate regime that is much drier and warmer.

In El Nino years, the southern Pacific Ocean currents reverse the normal east to

west direction, with major impacts on climate across the globe. Indonesia and

Australia, instead of enjoying the low-pressure system that brings tropical

rains, find themselves burning in heat waves and having to endure

drought-conditions. On the other side of the Pacific, countries such as Peru

find themselves suffering torrential rain and warm coastal waters that keep the

nutrient-rich cold waters of the Humboldt Current at bay, with plummeting

fish-catches. During El Nino years, the Amazon tends to dry out as the

rain-bearing air masses of the east to west circulation across the equatorial

belt are weakened and deflected. Moreover, it is likely to prove highly

destructive

to the forest, through causing it to dry out, die-back and become extremely

vulnerable to fires.

 

 

As the forest withers back, its mass of carbon, some 200 tonnes for each

hectare, is decomposed into carbon dioxide and methane, so building up still

more the greenhouse gases in the atmosphere. With the forest virtually all gone,

more than 70 billion tonnes of carbon gases will find their way into the

atmosphere. From their projections of the consequences of greenhouse gas

build-up, Peter Cox and his colleague Richard Betts at the Hadley Centre are

projecting average global terrestrial temperatures to go up by nearly 9 C before

the end of this century from the pre-industrial levels of 150 years ago. That

level of warming was last evidenced more than 40 million years ago, when neither

of the Poles had permanent ice (see “Back to the future for Gaia”, this series)

Sea levels were then more than a hundred metre higher than today. At current

greenhouse gas emission rates we have a few decades at best before the forest

begins its inexorable process of die-back and decomposition.

 

 

The current frenzied destruction of the rainforest is very likely to hasten the

total collapse of the Amazon. Thunderstorms are the key to the survival of the

forest because they bring essential rain, in some parts of the Amazon, as in

Colombia, to the tune of 40 feet a year. Cut the forest down and rainfall

dwindles. That causes still more of the forest to die, so reducing rainfall

still further and bringing about a vicious cycle of spreading degradation as

fires begin to rage out of control. Recent research indicates that more

thunderstorms then brew because of the soot and ash in the air. The result is

more fire-inducing lightning strikes.

 

 

Climatologist Roni Avissar has discovered that the loss of rainfall is not a

smooth process related directly to the loss of forest. On the contrary,

interspersed clearings between large areas of forest cause rainfall over that

region to increase by as much as 30 per cent. The reason is that the clearing

heats up during the day, considerably more than the forest, which cools itself

through processes of evapo-transpiration. A mass of air then rises over the

clearing, being replaced by cooler more humid air that is drawn in from the

surrounding forest. As the now-moistened air rises it convects into massive

cumulo-nimbus thunderstorm clouds that then cause powerful downpours to drench

the land around. On that basis, modest-size clearings are not a disaster. The

forest can cope. On the other hand, make the clearing too big, say more than 100

kilometres across, and the forest can sustain its humidity no longer. Literally,

the convection process runs out steam and the number of

rain-bearing thunderstorms drops dramatically. This is yet another example of

the non-linear, threshold effects that can precipitate abrupt change.

 

 

We are now perilously close to the critical point in certain areas of the

Amazon, such as in Para, Rondonia and the Mato Grosso, when any further loss of

forest will lead to a dramatic decline in rainfall. And that, says Avissar, will

have a direct and dire impact on the United States. His models show rainfall

declining by as much as 15 to 20 per cent over agricultural regions in the

United States during the critical growing months - shades of the Dust Bowl era

all over again - once the Amazon collapses as a rainforest system.

 

 

Whether it likes it or not, the United States is threatened on both counts.

First, because within decades from now the Amazon is likely to self-destruct

through being sucked dry by agro-industry. Second, the accumulating impact of

greenhouse gases in the atmosphere, is likely to lead within the same time-span,

to a sudden switch in air mass movements over the Pacific and the Americas.

Those El Nino -like changes will also cause a drying-out, accentuating the

impact of those same agro-industrial clearings.

 

 

We don’t have to let it happen. To date, the United States has acted with

supreme selfishness in failing to ratify the Kyoto Protocol and so reduce its

excessive greenhouse gas emissions. It now needs to act with equal selfishness

in signing up to such Protocols; its own future is at stake. That applies to all

of us, in Europe, Asia, the Americas. We have a decade at best to get our

emissions in order. But, in no less measure we must all act to ensure that the

greater part of the Amazon is conserved. The reasons are primarily for

safeguarding our climate. In so doing we would naturally conserve its

extraordinary biodiversity - a diversity of forms that holds the fabric of the

forest together and is the key to a safer world.

 

 

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General Enquiries sam

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