Melanie Lenart, Ph.D.: Environmental Scientist and Writer

Q & A with Melanie Lenart


cover of book, Life in the Hothouse1. You say the Earth is a living planet that has some means of controlling its temperature. Could you explain this?
This idea has fascinated me since 1989, when I read James Lovelock’s book, Gaia, right before moving to tropical Puerto Rico just in time for Hurricane Hugo. Lovelock proposed that we view our planet as a living system, which
he called Gaia. He noticed that the atmosphere of our planet differs from that of lifeless planets, such as by having far more oxygen proportionately and far less carbon dioxide. In other words, our air carries a signature of life. These ideas took on new meaning for me when I saw how quickly Puerto Rico’s forests rebounded after taking such a battering from the hurricane. It made me realize that, on its own, Nature is more powerful than we sometimes think. Plants have been taking up carbon dioxide and releasing oxygen since they evolved. And life’s influence on heat-trapping carbon dioxide affects climate. Scientists continue to refine Lovelock’s Gaia theory, which some call Earth system science. In Life in the Hothouse, I explain and expand upon these explorations. The concept helps explain why it’s logical for forests and wetlands to expand as the planet warms up.

2. What do you mean, the forests and wetlands expand? Doesn’t climate change threaten to destroy these systems as temperature climbs?
Well, first let me clarify that to say that forests and wetlands have expanded in warmer climates of the past, before humans were around with our axes, livestock and cities. Ice ages generally were dry and dusty outside of a few
sweet spots, which included the U.S. Southwest. It’s natural for forests to expand as temperatures thaw out the frozen places so tree roots can take hold, and for wetlands to expand as sea level rises. That’s assuming that cities
or farms aren’t blocking the way. Along with the warming temperatures, two other main reasons are behind this expansion. First, warmer air holds more moisture, so the world as a whole gets more precipitation. We’re already
seeing a tendency toward more intense storms. Look at all the snow in the East this past winter – that amount of snow is more likely with input from relatively warm air. Second, the extra carbon dioxide in the air serves as plant
food. Think about it. Plants create their tissues — basically carbohydrates — out of carbon dioxide and water. So you can see how having more of both of these around would generally boost plant growth. Water is really key
here. The nice thing is, having more carbon dioxide in the air actually improves a plant’s ability to conserve water. The expansion of forests and wetlands, in turn, helps balance the temperature by converting carbon dioxide into carbohydrates in plants and soil.

3. Are you saying we don’t need to worry about climate change — that Nature, or Gaia, will do what it takes to keep our climate in a safe range?
Actually, what is a safe range for the planet as a whole could be quite destructive for a society trying to live on its surface, not to mention many other species living in a particular place on Earth. Consider that during past
hothouses when the planet was ice-free, sea level stood 300 feet higher than it is today. Obviously that would have a serious impact on many islands and cities. Then there’s the issue of stronger hurricanes during hothouses —
there’s some indication that these storms were off the charts by our current standards during the mid-Cretaceous hothouse about 100 million years ago. And don’t forget, the warmer air that picks up more moisture not only can
make storms more intense – it also can make droughts more extreme. Add to that what shifting climate will do to world agriculture and other support systems, and you can see that we’ve got some serious problems on our hands if we let this warming carry on. Still, we have much to learn from exploring what our planet did during past hothouses and ice ages. We can take a lesson from what the planet does naturally and apply it so society can thrive as much as possible in these changing conditions.

4. So what do you recommend that society, and individual people do, to “thrive as much as possible in these changing conditions”?
Well, given that forests and wetlands would naturally expand in a warming climate, it makes sense for us to promote the growth of trees and the restoration of wetlands where they would occur naturally. Forests and
wetlands collect carbon dioxide, thus clearing the air of some of this heat-trapping gas. As it happens, forests and wetlands also have other features that make them important in warm climates. Trees provide shade and cool the
air by evaporating water. They also reduce wind speeds, which can be especially important in areas susceptible to hurricanes. Forested wetlands do these same things. Plus wetlands and soils in general have an amazing ability to purify water — they act like cleansing carbon filters. Globally, we can encourage the expansion of these systems by setting up financial incentives to support their many services, from collecting carbon dioxide to cooling the surface to cleaning the water. Countries can do this as well. Even individuals can plant trees, or work to protect or restore wetlands.

5. Does this mean we can have a livable planet without cutting our fossil fuel use?
To keep global warming in a range manageable for society, it is absolutely crucial that we reduce our fossil fuel use, as individuals and as a world. Right now, our planet’s natural systems are already pulling down more than half
the carbon dioxide we’re releasing by burning of oil, coal and gas. And they’re recollecting all the carbon dioxide released by the burning and harvesting of forests around the world. But the plants can’t fix the problem when we
continue to add more and more carbon dioxide to the air every year. There’s no doubt we need to slow down the pace of adding greenhouse gases to the air if we want to stabilize climate within a range that suits society. At the
same time, we also need to recognize the long-standing role played by plants in regulating climate. What’s more, we need to consider some of the planet’s physical responses to the temperature rise, such as more intense storms,
so we can prepare for them. Forests and wetlands can help with that too.

6. What do you say to the people who think the planet is going through a natural warming cycle, that the rising temperatures are just part of that?
You know, I think this recent revival of climate skepticism is going to be relatively short-lived. The foibles of a few individuals or flaws in a few studies just won’t stand for long in the face of the erratic but generally upward
trend of warmer temperatures being documented in so many different ways, from the early budding of flowers and migration of birds and butterflies to the melting of glaciers. It’s good news that the threat of the Himalaya’s
glaciers melting by 2035 was recognized as an error. But that doesn’t explain away the extensive melting around the North Pole, where summer ice extent reached a record low in 2007. Even that will vary from year to year, as
climate does. At some point, though, we’ll have another year of record-breaking heat that will turn these skeptical voices into background noise. The climate system is complex, and subject to ups and downs for reasons other than greenhouse gas levels. Yet a look back into deep time — in Life in the Hothouse, I focus on the past 100 million years — makes it clear that higher carbon dioxide levels and higher temperatures move together. There’s no reason to think modern times are an exception to this long-standing rule.

University of Arizona Press




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