Category Archives: Climate change

Can animals evolve to survive climate change?

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Many who might be skeptical that climate change is a problem that results from Human activities will say, as a last refrain:

“Oh, anyway… animals can just evolve to survive rising temperature.”

But is this true?

funny-hot-dog-melting-picsCharled Darwin had a dreadful time trying to convince his Victorian peers that evolution by natural selection was a real process in nature. This is because he could not demonstrate unequivocally that is was happening. And the reason that he could not demonstrate that it was happening is that it happens slowly.

I mean, part of the process of evolution results when organisms adapt to new and changing environments. This adaptation takes place over hundreds or thousands of generations. The snow leopard will not just simply decide that it’s too warm and shed its fur so that all is hunky-dory.

Thinking about Human generation times – arguably 20 years – hundreds of generations means that it takes 5000-10000 years to notice even very small changes that result from mutation of genes that might confer an evolutionary advantage in a given situation. Most organisms have shorter generation times but even the smallest adaptations gotten through evolution will realistically take 1000s of years.

I saw a calculation recently that showed that animals can ‘evolve’ at a rate that would make them able to adapt to temperature change of 1 degree celsius per million years. Present calculations show that our average temperature on earth will likely rise by 4 degrees celsius by the end of this century. Evolution needs to work, uh, let’s see… (4 degrees in 87 years = 1 degree in 21.75 years, and 1,000,000 / 21.75 = 45977), 46,000 times faster than it does now. That isn’t going to happen.

The funny thing is that an average temperature rise of 4 degrees doesn’t seem like that much to us. It will have devestating consequences for our planet, however. Ice sheets will melt and the water cycle will be thrown completely out of kilter with consequences like worsening weather, flooding, and drought like we are starting to experience now.

familyAnimals and plants that have evolved to survive in their special environment (and that’s generally what evolution has done) might survive the onslaught of climate change for a while by moving to adjacent environments where it is (choose one – wetter / drier / warmer / colder) but that is a short-term fix.Plants and animals that are adapted to survive in desert environments are separated by hundreds of millions of years of evolution from those that are adapted to survive in very wet conditions.

Our snow leopard really won’t find the prey items that it needs to survive if its habitat warms, and it can’t simply pick up and find a new home like the Bevely Hillbillies did (Kin folks said, Jed, move away from there…)

Forests using less water because of climate change

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This article was originally published in Conversation logoThe Conversation

and in Ars Technicaars-technica-logo

Forests using less water because of climate change – a good thing?

Global warming is primarily driven by increasing emissions of greenhouse gases from human activities. Chief among these gases is carbon dioxide (CO2), which warms the planet by trapping heat that would otherwise radiate into space.

9kvm83bg-1374505630But carbon dioxide has effects on things other than the climate. In the journal Nature, Trevor Keenan of Macquarie University and his colleagues report that trees in some forests are using less water to maintain growth than they did only 20 years ago. This puzzling finding has been attributed to the increased levels of CO2, which trees utilise as their carbon source.

Instruments placed in various US forests have been measuring CO2 and water concentrations in the air for many years. These measurements have been correlated with the amount of CO2 locked up by trees over the same period to show that forests have become more efficient at storing carbon. What is more important is that the measurements suggest that the increase in efficiency of storing carbon is six times greater than would be expected if it was just proportional to the increase in atmospheric CO2 concentration during the same period.

Increased CO2 availability means that trees have to restrict the opening of their breathing pores (stomata) so that CO2 levels inside their leaves remain constant. But this has additional consequences for the trees. Smaller pores means less water evaporates from their leaf surfaces through these stomatal openings. This effect has been called the “CO2 fertilisation effect”, which means plants can utilise more CO2 to make more carbohydrates, like cellulose and sugars, while using smaller volumes of water overall than previously required.

The fine balance between CO2 uptake and water loss is critical for plant survival. Early predictions by climate scientists were that increasing temperatures would devastate forests. That is because elevated temperatures increase the rate of evaporation and transpiration at leaf surfaces, potentially causing trees to suffer from “water-stress”. Instead, this paper suggests that increased efficiency of water-use by forests might mean that water does not become a limiting factor in productivity as temperatures rise.

This new finding seems like unadulterated good news, therefore, until you factor in the effect that water usage by forests has on components of the ecosystem. Trees move an incredible volume of water from the ground into the atmosphere. That water then forms rain, which helps the connected ecosystem thrive. Large forested areas play a very important role in the water balance and ecology of most agricultural land on Earth.

Keenan and his colleagues examined 21 forest sites going back as much as 20 years, with their data limited to the temperate and boreal forests of the Northern Hemisphere. Although this is still a relatively small sample size, this work will probably result in a flurry of research activity to establish what will happen to plant primary productivity in other areas in response to elevated CO2. Keenan said: “We’ve examined the trend upside down and inside out as much as we can, and it is wholly robust.”

Climate scientists use data from studies such as this one to build long-term computer simulations that help them examine potential effects of alterations in variables like temperature, ocean currents and rainfall. Decreased volumes of water being moved by transpiration into the atmosphere will now be added as an input in these simulations in an attempt to predict what the medium and long-term effects of the new observations might be.

On the one hand, more consumption of CO2 by forests will help stem global warming. But on the other hand, less water circulated through more efficient use by trees will mean that non-forest ecosystems may get into trouble.