Future of Earth: Desert or Explosion of “Global Greening”?

In an ancient lake bed at Southern Hemisphere scientists studying fossil leaves found out the mechanism of the plants living during the Miocene Epoch in which the world used to have an elevated level of carbon dioxide in the atmosphere. It gives a hope that with an increased rate of carbon dioxide in the air, instead of seeing our beloved earth turning into a barren field the world may see a “Global Greening” effect. Although there may still be other devastating global warming effects such as rising sea levels, more severe weather and other consequences of climate change.

The ancient lake bed is situated at Foulden Maar, an extinct volcanic crater near the city of Dunedin on New Zealand’s south island. The crater was formed during the early Miocene about 23 million years ago and hosted a lake that slowly filled in and preserved the remains of the subtropical rainforest growing there. The leaves of the Miocene trees were mummified in the lake being layered between the hard remains of silica rich algae.

Foulden Maar, an undisturbed fossil site

Previous researches have revealed that though elevated carbon dioxide level led to warmer temperature during the Miocene, there had been certain plants which were able to use water more efficiently under the conditions of high CO2 level and temperature. But this study is the first one to provide with results bearing empirical evidence of a carbon dioxide fertilization effect in the fossil record. The CO2 fertilization effect is the increased rate of photosynthesis in plants that results from increased level of CO2 in the atmosphere.

Mummified leaf

Being mummified it served a great opportunity for the scientists to make anatomical and chemical measurements on the leaves from which they could easily get a clear vision of the climatic and atmospheric conditions at the time when the forest was growing. The fossils leaves are from a time where global temperature was on average about 5-6 degrees celsius higher than today and was almost 8 degrees celsius warmer in southern New Zealand. Back then the amount of carbon dioxide in the air was between 450 & 550 parts per million. The current atmospheric carbon dioxide concentration is 411 parts per million and by 2040 it may reach about up to 550 parts per million. Hopefully by that time plant species may begin to behave in the same way the ancient did in Foulden Maar.

mouth shaped stomata of fossil leaf, through which it took in carbon dioxide and released water

Researchers found that the Miocene trees were unusually efficient at sucking in carbon through stomata without leaking much water through the same route. These findings can therefore provide researchers with a model for what changes in plant function might need to look like for some species in the future. We know, when CO2 level rises, many plant species increase their rate of photosynthesis because they can more efficiently remove carbon from the air and conserve water while doing so. But even these species probably going to stop photosynthesizing at a CO2 level like the Miocene epoch. 

The characteristics of future plant species will be or will need to be-

  1. Better at consuming carbon dioxide through stomata.
  2. Having increased rate of photosynthesis even in high COlevel (like atmospheric condition having up to 550 parts per million CO2) and temperature.
  3. Becoming more drought tolerant.
A study of NASA showing carbon dioxide fertilization effect from 1982-2015

Data from NASA satellites shows a “Global Greening” effect mainly due to rising levels of CO2 released by human activities over recent decades. It has been estimated that a quarter or a half of the planet’s vegetated lands have seen increases in leaf volume on trees and plants since 1980. The effect is expected to continue as CO2 level rise. 

Given enough time for adaptation this may lead to an expansion of earth’s forests. Although the current speed of change makes it difficult for plants to adapt. Only time will say if the life of earth will win or lose at the end.

Even if “Global Greening” effect happens at a great expanse and instead of turning into a desert the world turns to be much greener, other effects of global warming such as rising sea level, melting glaciers, severe weather, flood, increasing rate of natural calamities may still be haunting on earth.


Reference

Journal Climate of the Past of EGU (European Geosciences Union)

Carbon Dioxide Fertilization Greening Earth, NASA

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About Tarannum Ahsan

Tarannum Ahsan
I'm a student of department of botany at University of Dhaka. I'm learning a lot of new interesting things about different spheres of botany and I'll keep updating about them to keep your knowledge of nature enriched.

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