Tree fos­sils re­veal Antarc­tica had for­est be­fore time of the di­nosaurs

Tehran Times - - SCIENCE -

The now frozen Antarc­tica had a for­est dur­ing the Per­mian Pe­riod, be­fore the time of the di­nosaurs. How do an­cient po­lar for­est dif­fer with the mod­ern day forests we see to­day?

Fos­sil frag­ments of an­cient trees in Antarc­tica sug­gest that the now frozen con­ti­nent was not as bar­ren as it is to­day. Ev­i­dence that re­searchers gath­ered af­ter climb­ing the slopes of the McIntyre Promon­tory in the Transantarc­tic Moun­tains showed Antarc­tica had a thriv­ing for­est be­fore the di­nosaurs walked on Earth.

Af­ter look­ing for ev­i­dence of the cold con­ti­nent’s po­ten­tially lush past, Univer­sity of Wis­con­sin - Mil­wau­kee (UWM) re­searchers found fos­sil frag­ments be­long­ing to 13 trees that are more than 260 mil­lion years old.

A frozen wilder­ness

“We take it for granted that Antarc­tica has al­ways been a frozen wilder­ness, but the ice caps only ap­peared rel­a­tively re­cently in ge­o­log­i­cal his­tory,” Jane Fran­cis, from the Univer­sity of Leeds, has said.

The age of the fos­sils re­vealed of for­est in Antarc­tica at the end of the Per­mian Pe­riod, the time be­fore the first di­nosaurs emerged.

About 251 mil­lion years ago, the Per­mian Pe­riod ended in a mass ex­tinc­tion event as the Earth’s cli­mate con­di­tions rapidly shifted. Over 90 per­cent of the Earth’s species were wiped out, and these in­cluded the po­lar forests.

The vol­canic erup­tions in Siberia over a pe­riod of 200, 000 years may have re­leased mas­sive amounts of green­house gases. Sci­en­tists now think that the in­crease in the amount of at­mo­spheric green­house gases, such as the Earth -warm­ing meth­ane and car­bon diox­ide, is be­hind the Per­mian-Tri­as­sic ex­tinc­tion.

At the end of the Per­mian Pe­riod, Antarc­tica was more hu­mid and even warmer when com­pared to what it is to­day. It was also part of the Gond­wana su­per­con­ti­nent that spanned the South­ern Hemi­sphere and also in­cluded what is now the Ara­bian Peninsula, Aus­tralia, In­dia, Africa and South Amer­ica.

Re­searchers said that the for­est, which likely spanned across the whole of the Gond­wana con­ti­nent, likely had a mix­ture of ferns, mosses and a now ex­tinct plant known as Glos­sopteris.

Fos­sil forests

Re­searchers re­vealed that the fos­sil forests were dif­fer­ent com­pared with present day forests. Forests dur­ing the Per­mian pe­riod po­ten­tially had a low di­ver­sity of plants with par­tic­u­lar func­tions that con­trib­uted to the way the forests re­sponded to changes in the en­vi­ron­ment.

These an­cients forests were in con­trast to the char­ac­ter­is­tics of mod­ern day high-lat­i­tude forests that are marked by greater plant di­ver­sity.

Un­for­tu­nately, the ro­bust forests did not sur­vive the high con­cen­tra­tion of green­house gas dur­ing the mass ex­tinc­tion.

The re­searchers plan to re­turn to the site to look for mass ex­tinc­tion event de­posits that can shed more light on how the forests re­sponded to the ris­ing level of car­bon diox­ide in the at­mos­phere.

“With fur­ther study, we can bet­ter un­der­stand how green­house gases and cli­mate change af­fect life on Earth,” Gul­bran­son said.

These an­cients forests were in con­trast to the char­ac­ter­is­tics of mod­ern day high­lat­i­tude forests that are marked by greater plant di­ver­sity.

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