Global warm­ing fa­tal to trees

Austin American-Statesman - - BALANCED VIEWS - Hal­ter is a broad­caster, writer and bi­ol­o­gist. His lat­est books are: ‘The In­sa­tiable Bark Bee­tle’and ‘The In­com­pa­ra­ble Honey­bee.’


forests are breath­tak­ing. In fact, trees are ef­fec­tively the great­est CO2 ware­houses to have ever evolved on Earth. For ev­ery met­ric ton of wood cre­ated, 1.5 met­ric tons of CO2 is ab­sorbed and 1 met­ric ton of oxy­gen is re­leased.

Fright­en­ingly, Earth’s forests are dy­ing from a warm­ing world.

Re­cently re­searchers once again sent an SOS call to denizens of Earth — drought con­di­tions are plac­ing deadly wa­ter­stress on forests around the globe. More­over, Earth’s forests and myr­iad “ecosys­tem ser­vices” that pro­vide all life are ap­proach­ing an ir­re­versible tip­ping point.

In 2009 the In­ter­na­tional Union of For­est Re­search Or­ga­ni­za­tions came to a very bleak con­clu­sion: “The car­bon stor­ing ca­pac­ity of Earth’s forests could be lost en­tirely if the planet heats up 4.5 F above pre-in­dus­trial lev­els.” So far, we have in­creased by about 2 F, which means we are al­ready well on our way to­ward this fate­ful thresh­old. The re­sult of cross­ing it would be an un­in­hab­it­able world.

Ris­ing green­house gases are also wreak­ing havoc in the trop­i­cal forests, more specif­i­cally in the Ama­zon. The heart of the Ama­zon has not evolved to con­tend with fierce winds, nor with drought. In 2005 a vi­cious com­bi­na­tion of cli­mate dis­rup­tion oc­curred across a 733,600 square miles of land. In Jan­uary, an in­tense thun­der­storm, span­ning 62 by 124 miles, ripped through the whole Ama­zon Basin. On its path, the storm lev­eled be­tween 441 mil­lion and 663 mil­lion trees — or the equiv­a­lent of 23 per­cent of the es­ti­mated mean an­nual car­bon ac­cu­mu­la­tion ca­pac­ity of the Ama­zon for­est.

Later in 2005 a “one-in-100 year” drought oc­curred. Not only did the Ama­zon fail to ab­sorb 1.5 bil­lion met­ric tons of CO2 that year, but also over the next decade it’s re­leas­ing ap­prox­i­mately 5 bil­lion met­ric tons of CO2 from de­com­pos­ing trees. And as the Ama­zon forests die, the Earth also loses its vast cloud-mak­ing machines forc­ing it to ab­sorb in­com­ing so­lar ra­di­a­tion rather than re­flect it.

In 2009, the United States alone emit­ted 5.4 bil­lion met­ric tons of CO2 from fos­sil fuel use. Sci­en­tists have doc­u­mented that green­house gas emis­sions have sig­nif­i­cantly al­tered global cli­mate — in­creas­ing the fre­quency, du­ra­tion and/or sever­ity of drought and heat stress in 88 forests on ev­ery wooded con­ti­nent on Earth. All for­est types are suf­fer­ing from a lethal com­bi­na­tion of at least three fac­tors: in­sects and dis­eases as­so­ci­ated with el­e­vated tem­per­a­tures; the dry­ing out of plants; and car­bon star­va­tion, that is, water-stressed trees are un­able to pho­to­syn­the­size, or make food.

Ex­treme droughts in North Africa are killing Atlas cedar from Morocco to Al­ge­ria. Heat and drought are bat­ter­ing the high-el­e­va­tion trop­i­cal moist forests in Uganda, moun­tain aca­cia in Zim­babwe and cen­turies-old aloe plants in Namibia. Trop­i­cal forests of Malaysia and Bor­neo have also suf­fered sig­nif­i­cant death. Drought has also lam­basted the trop­i­cal dry forests of north­west and south­west In­dia, fir in South Korea, the ju­nipers of Saudi Arabia, and pine and fir in cen­tral Turkey. Ex­ten­sive ar­eas of for­est in two re­gions of China have now been rec­og­nized as be­ing at a high threat of mor­tal­ity in the en­su­ing years. Rus­sia too has iden­ti­fied 187.8 mil­lion acres of high-threat forests whose trees are se­verely stress by drought. Aus­tralia has seen wide­spread death in aca­cia wood­lands and eu­ca­lypt and Co­rym­bia forests. New Zealand has doc­u­mented drought-in­duced death in high-el­e­va­tion beech forests. Oak, fir, spruce, beech and pines across West­ern Europe are dy­ing too.

Ris­ing green­house emis­sions are el­e­vat­ing tem­per­a­tures and the oc­cur­rence of droughts across west­ern North Amer­ica. In turn, this is fu­el­ing the largest na­tive bark bee­tle epi­demic in mod­ern or past times (dat­ing back over 200 mil­lion years). In­stead of ab­sorb­ing CO2 about 30 bil­lion ma­ture trees are de­cay­ing and adding green­house gases to the ever-ris­ing at­mo­spheric pool.

Earth’s forests are its life­sup­port sys­tem.

We need a car­bon-tax in Amer­ica and world­wide. And we need it now.

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