Life in the Hothouse

by Bryan Walker on May 5, 2010

“Wetlands are wastelands” was the explanation the chair of a local trust in my city gave for opposing a grant to a wetlands restoration project. He’s a rabid climate change denier and hence unlikely to read Melanie Lenart’s recently published book Life in the Hothouse: How a Living Planet Survives Climate Change. If he did he would discover how wrong he was. Not that he needed wait for her book: it has been evident for many years that wetlands are vital to ecological health. So are forests, which play an equal part in Lenart’s explanation of how Gaia, or, if you don’t like metaphor, the complex interacting system of the biosphere, responds to maintain a temperature within a range suitable for life. A scientist with a background in journalism, Lenart is well placed to provide a coherent account for the general reader of the work of a host of researchers who have explored some of the intricacies of response to warming in Earth’s ecosystems.

She opens with an interesting account of hurricanes as both a symptom of global warming and one of its cures. A warmer world is likely to mean they are more intense. She considers them from the perspective of their cooling function, helping to shift heat away from the tropics. Their destructive power, which is clearly pictured, paradoxically boosts plant life in the sea and on land through sediment stirring and transfer and so aids the drawing down of carbon dioxide from the atmosphere. They also contribute to carbon sinks by burying logs, soil and sediment in landslides, the ocean, and anywhere they can better escape decay.  In these respects they are one of Gaia’s natural defences to rising temperatures.

A chapter on circulation patterns explores many of the ways in which precipitation has increased in warmer climates in the past and considers the contribution of such features as the Hadley circulation between the equator and the sub-tropics. The comparative dryness of the ice ages came as a surprise to climatologists. The evidence Lenart adduces spanning the ice ages to ancient hothouses makes it clear that global precipitation rates increased as the climate warmed. This she sees as helping boost a Gaian response to changing climate, namely increased plant growth.

There follows a survey of carbon dioxide uptake by plants and trees and how various forests fared in past climates.  More carbon dioxide has meant more growth.  More precipitation and more warmth has helped that growth. The contribution of plant life in taking carbon dioxide from the air is significant.  The world’s trees alone hold nearly as much carbon as the atmosphere. In this way life becomes part of the Gaian attempt to regulate temperature.

Soils and wetlands also soak up excess carbon dioxide. Wetlands’ special talent for this is related to their remarkable productivity combined with their slow decay rates. Decay stalls in stagnant waters, including the decay of organic material from far and wide that ends up in wetlands because of their low-lying position.  The world’s soils are considered by some researchers to hold three times the amount of carbon in the vegetation growing on them. Lenart explains in detail how this happens, with coal being the prime example of the process in the distant past: carbon well sequestered until we started to extract and burn it.

Weathering is the final process Lenart considers as another method by which Earth balances its carbon dioxide ledger. It takes place over a long term and is perhaps not likely to be of much assistance in dealing with our present problems, but it’s a fascinating sequence she describes as nature’s version of acid rain works to break down rocks with a resultant carbon storage in the sea – for limited periods in the case of limestone, but more permanently in the case of basalts and granites, at least until it becomes volcano fodder.  Weathering speeds up in hot, humid climates, pulling more carbon dioxide out of the air when there is more than usual there.

I’ve scratched the surface of chapters that are packed with interesting detail about both past and present.  Lenart does an excellent job of pulling together information from numerous studies, often updated by direct communication with the experts involved, and building it into a sustained overall picture. The story is enlivened by some of her own direct experience in forest and desert. The good science writer or journalist is able to render the general reader this service in a way that the specialists engrossed in their work would be harder put to provide.

The book’s strands come together in a chapter titled systematic healing. Lenart fully subscribes to the recognition that our use of fossil fuels must be drastically cut. She’s not suggesting any alternative to that. Her particular interest is rather in how we can also work with the natural systems her book has been describing to help moderate the warming and soften the severity of its impacts. She acknowledges that is difficult in our current economy where the bottom line ignores environmental costs and overlooks environmental services. In fact the services provided to humans by wetlands and forests, including urban forests, go well beyond carbon counting. Urban forests provide shade and evaporative cooling valuable in times of elevated heat.  She refers to the efforts in Chicago to plant rooftops and increase ground tree and shrub planting as an example other cities might follow. Urban greenery not only cuts heat, but provides habitat for birds and other wildlife, insulates against noise, offers recreational possibilities and reduces air pollution including carbon dioxide. There is even some evidence that it cuts crime!

Forests on a larger scale  promote rainfall. Forests and wetlands slow down winds. Wetlands absorb storm surge and slow flooding rivers. They also purify water. Biodiversity and genetic diversity are greatly assisted by wetlands and estuaries. These and many other services are additional to the carbon capture contribution made by forests and wetlands, the protective shield a warming planet produces. Our current experiment is to interfere with the development of these natural protective processes. We are lowering biomass, lowering water tables, lowering the quantities of weathering product reaching the sea through extensive development, logging, groundwater pumping, and river diversion.

Lenart metaphorically shudders at the thought of some of the geo-engineering fixes being proposed. Why build artificial trees to chemically remove carbon dioxide from the atmosphere, she asks, when Gaia can make trees that provide food and shelter, sunscreen and windbreaks, and flood-control and drought-prevention services even while collecting carbon dioxide and other pollutants? She looks to a variety of forest and wetland restoration projects to restore these key systems. The more we can count on forests and wetlands to stabilise the carbon dioxide drawdown, the less pressure we put on oceans to take up the gas and thus increase their acidity. And the more we pull down greenhouse gases into forests, their soils and wetlands, the less need the planet will have for cooling hurricanes and floods. Life gets better at all scales when we boost Gaia’s natural defences.

{ 6 comments… read them below or add one }

bill May 5, 2010 at 9:11 am

One of my functions is as a revegetation officer for a large peri-urban council here in Australia. I've been there for around 12 years – yes, that is unusual; diverse and interesting permanent part-time positions are nothing to be sneezed at! – and in that time the transition in our engineering department with regard to managing stormwater has been remarkable.

The old days of designing giant concrete chutes designed to run water 'out of the environment' as quickly as possible are long gone. Wetlands, 'naturalised' watercourses and ASR (Aquifer Storage and Recovery) projects are now the rule. And every new development seems to centre on a wetland (there are some problems here, of course, but my point is that the generally positive view of them is striking.)

An adjacent council has also developed a national-benchmark storm-water management and wetland complex, and has even processed water to potable standard, though public resistance to actually drinking it is still strong! (It was an election issue only a couple of months ago. We'll have to do it eventually, I suspect.)

(We also have an extensive network of reclaimed water from the city's major sewage treatment works that irrigates much of the large horticultural zone that lies in the district.)

Landscaping and horticulture has also shifted to a very strong focus on sustainability, including the incorporation of local-native species where appropriate, and low-water demand, non-invasive species otherwise. Our successes have been sufficient for interviews with two of our staff members to have been incorporated into the state Museum's new Biodiversity Gallery's introductory video that greets visitors as they enter the display!

Sounds like a very interesting book.

Macro2 May 5, 2010 at 8:38 am

And the only encouragement to regenerate wetlands from central govt is zip and from local govt is $2000 towards fencing. (Although depending on the region the possibility of sub division potential is a definite carrot. But only developers really embark on regeneration of wetlands with that in mind.)

I shall have to read it! Just finished reading "Mindfully Green" by Stephanie Kaza Professor of Environmental Studies a University of Vermont. :)

bill May 5, 2010 at 9:11 am

One of my functions is as a revegetation officer for a large peri-urban council here in Australia. I've been there for around 12 years – yes, that is unusual; diverse and interesting permanent part-time positions are nothing to be sneezed at! – and in that time the transition in our engineering department with regard to managing stormwater has been remarkable.

The old days of designing giant concrete chutes designed to run water 'out of the environment' as quickly as possible are long gone. Wetlands, 'naturalised' watercourses and ASR (Aquifer Storage and Recovery) projects are now the rule. And every new development seems to centre on a wetland (there are some problems here, of course, but my point is that the generally positive view of them is striking.)

An adjacent council has also developed a national-benchmark storm-water management and wetland complex, and has even processed water to potable standard, though public resistance to actually drinking it is still strong! (It was an election issue only a couple of months ago. We'll have to do it eventually, I suspect.)

(We also have an extensive network of reclaimed water from the city's major sewage treatment works that irrigates much of the large horticultural zone that lies in the district.)

Landscaping and horticulture has also shifted to a very strong focus on sustainability, including the incorporation of local-native species where appropriate, and low-water demand, non-invasive species otherwise. Our successes have been sufficient for interviews with two of our staff members to have been incorporated into the state Museum's new Biodiversity Gallery's introductory video that greets visitors as they enter the display!

Sounds like a very interesting book.

Macro2 May 5, 2010 at 9:51 am

No! permanent part time is NOT to be sneezed at! I have one as well! :) Soon to retire to the beach though….. (fingers crossed).
All new developments here also have their obligatory "wetland" – one commercial sub – division we recently surveyed even had "water gardens" instead of cess pits for storm water run – off. But all very mono-culture. Mostly sedge (the variety that the nursery has growing at the time), a cabbage tree or two for variety and maybe some flax and toi toi..
We have reduced the wetlands in NZ to just 5% of the original extent – and I gather that is not uncommon world wide. In Auckland which had extensive wetland areas 150 years ago, there is just ONE natural wetland left – by Bethels Beach. Farming accounts for a large part in wetland destruction. You can't farm wet land – so its drained. But the recent wetland sub division provisions have made a difference. I know of one dairy farm just north of Helensville where a significant inland wetland has meant the owner has fenced it off and has subdivision potential for up to 100 rural dwellings. Now that is an offer you can't refuse! These regenerating wetlands are more the real thing. They need time and management. But even after a few years the changes are significant.

bill May 5, 2010 at 10:36 am

Where I work one of the issues is that artificial wetlands probably now cover rather a larger area than natural ones did historically! At 450mm p/a – and declining – this could prove to be 'interesting'. (NOTE: New Zealanders – yes, that number refers to an average rainfall! I realise it might appear almost incomprehensibly small…)

But, as you're doubtlessly aware, Australians have devoted special attention to stuffing up river and wetland systems, and have succeeded marvellously (Hint: issue rather more permits for water than you have actual water).

For wetlands specifically less than 1% remain in the adjacent ranges; overall more than 70% have been destroyed across the state. Add to this the issue of it not raining anymore, which tends to have a negative effect even if the natural 'infrastructure' is still present. Much of the south-east of the state was a giant wetland complex – now it's a series of vineyards and drained pastures; both of which are very productive, and both of which face a serious salt problem.

Ah, retiring to the beach! Very nice. And if we wait long enough, it may come to us…

Macro2 May 5, 2010 at 11:14 pm

"Australians have devoted special attention to stuffing up river and wetland systems, and have succeeded marvellously (Hint: issue rather more permits for water than you have actual water)."

Bill we are slow but we are learning ( eg "demise" of Environment Canterbury) We may soon catch you up! Gareth might be in a better position to comment on this.

As for the beach coming to meet us we are 3 mins from the beach and 10 mins back. :). I calculate Greenland and a large part of Antarctica. But then that's not counting earthquakes – which have moved this part of the country substantially up and down. Well you can't have everything.

The effect of a "minor" drought has had a significant effect on wetland in the North here. Grasses are still holding up – but many wetland areas (ie wet 8 months of the year) are now dried out. This has depleted small water ways, ponds and "swamp" to dry dust, the bird life has disappeared, frogs and small native fish have been affected also. The established plants are surviving and hopefully with some rain in winter things will return to normal, but if this is a precurser of things to come for this part of the country it will mean a whole new rethink of how we manage our, until now, abundant water supply and our wetlands. Notably has been the need for kiwi to feed during the day – the ground being so hard and their food source burrowing deeper.

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