Tag: ecosystems

Life in the Hothouse

“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.

Climate compendium: important insights

Compendium“The Climate Change Science Compendium is a wake-up call. The time for hesitation is over”. So wrote Ban Ki-moon in his foreword to this UN Environment Programme publication released last week. The publication is a review of how climate science has evolved since the Fourth Assessment Report (AR4), and is based on some 400 major scientific contributions in the peer-reviewed literature or from research institutions since the deadline for inclusion in AR4 three years ago. It appears in response to the request of many governments and stakeholders for a snapshot update. Achim Steiner, the Executive Director of the Environment Programme makes it very clear that it doesn’t replace the painstaking rigour of an IPCC process, but he hopes it will provide important insights into the rapidly developing and fast moving realm of climate science so that the choices made by leaders in Copenhagen in December are informed by the best and the latest research available to the international community.

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Copenhagen 2: dangers ahead

cop_logo_1_r_editedThe second section of the Copenhagen synthesis report, Social and Environmental Disruption, discusses the dangers of climate change relating to society and the environment, noting that scientific research provides a wealth of relevant information which is not receiving the attention one might expect.    

Considerable support has developed for containing the rise in global temperature to a maximum of 2 degrees centigrade above pre-industrial levels, often referred to as the 2 degrees guardrail. The report however indicates that even at temperature rises less than 2 degrees impacts can be significant, though some societies could cope through pro-active adaptation strategies.  Beyond 2 degrees the possibilities for adaptation of societies and ecosystems rapidly decline, with an increasing risk of social disruption through health impacts, water shortages and food insecurity.

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Heatstroke

algae

Anthony Barnosky is a Berkeley University paleoecologist deeply concerned about what lies ahead for Earth’s ecological systems if we persist in heating the globe. His recently published book Heatstroke: Nature in an Age of Global Warming explains his concerns. Global warming with its own method of ecosystem demolition has joined the three other factors — habitat loss, introduced species and population growth — by which human activity has impacted badly on ecologies.

Yes, climates have changed in the past and species and ecologies have changed with them.  Many scales of climate change have occurred, from slow tectonic to the fast changes embedded within glacial and inter-glacial times.  Why should an ecologist worry about today’s global warming which is just one more scale? Barnosky has two reasons: one is the rate of change, which is way faster than anything in the past, the other is that the new climate will be hotter than that in which homo sapiens and many other animal species evolved.

Barnosky’s book is packed with examples of what is already happening and what it points to. As the climate warms many species already have to move to survive.  He quotes the result of one survey which showed a set of 99 species of birds, butterflies and alpine herbs which within ten years had shifted on average 6.1 kilometres poleward or 6.1 metres upward in elevation. Dying out on mountain tops is the fate or likely fate of the latter. He traces many other factors, such as the subtle interactions between climate, vegetation, and reproductive success for species such as reindeer, or the change of climate conditions to favour the fungus which kills harlequin frogs – in the tropical mountains of Central America they are now dying in unprecedented numbers because of this new interaction between species. Synchronisations which have served some species well are no longer able to be relied on – marmots in the Colorado Rockies are coming out of hibernation earlier, but heavier snow is taking longer to melt and the green shoots the emaciated marmots need to feed on are not ready. In the ocean he details many instances of marine ecosystems under serious stress from the double whammy of traditional human impacts such as pollution and overfishing now followed by global warming. Corals are a clear example.

Yosemite and Yellowstone National Parks, Kruger Park in Africa and Tambopata Nature Reserve in Peru, are among places Barnosky selects for closer attention. Small mammal species in Yosemite have changed how they live in the park, in a way that indicates some may be on the way out. Amphibians in Yellowstone are in decline. In Kruger between 13 and 20 of the 87 mammal species there today are projected to disappear by 2080. The Tambopata rainforest, along with many rainforests throughout tropical South America, has a 75% chance of being mostly savannah by 2080.

Barnosky devotes a fascinating chapter to what began as his big moment of realisation in a deep cave in the Colorado mountains in 1985. That moment turned into a fifteen year project for four large institutions, more than two dozen scientists and hundreds of volunteers.  They retrieved thousands of fossils deposited over nearly a million years by bushy-tailed wood rats who have the convenient habit of collecting odd objects they find lying around and bring them back to their nests. Among their favourite items are bones, some of them encased in the pellets regurgitated by birds or defecated by carnivores. In the eight feet of excavated layers in that cave was an invaluable record of the changing makeup of local species through the climate changes of the Pleistocene. The story of how the various layers were interpreted and dated is another of those intricate detective operations which mark the scientific interpretation of so many of the clues from the past still embedded in discoverable form.

Barnosky is always considered in his appraisals.  He gives due weight to the resilience of ecologies, and nowhere rushes to judgment. But he thinks we are in a time of accelerated extinction of species, and warns that it could be very large indeed. There were already pressures enough driving us towards dwindling biodiversity.  Global warming increases greatly the speed of the train on its way to mass extinction.

A sober chapter discusses the possibility of climate change acting as a selective force to stimulate the building of new species.  In the past, times of slow climate change seem to correlate with bursts of speciation.  But Barnosky points out that climate change today is at a rate which outpaces mutation rates of most animal and and plant species by a far greater margin than we have ever seen. Recombination within gene pools offers some possibility of evolutionary change, but it is limited without sufficient mutation. At the end of this discussion, engrossing for any lay reader with an interest in evolutionary processes, he concludes: “Global warming is not only doing its part to diminish biodiversity substantially within a century or so, it is also limiting the future evolutionary potential of Earth.”

Barnosky nevertheless insists on hope.  His final chapter centres not only on slowing down global warming but also on a programme for wilderness protection.  First we need to keep what we already have – the 12% of Earth’s surface now protected in some fashion to preserve nature. Second, climate-connection corridors must be provided for species movement. Third, new initiatives are required to minimize high-impact human land use, to create marine-based reserves before it is too late, and to consider the conceptual division of reserves into two functions – one kind devoted to the preservation of individual species and certain assemblages of species, the other devoted to the preservation of wilderness.

The alternative for humanity is the technological “termite-life” of ecological loss.

Barnosky writes with an easy style, combining clarity with a near-conversational level of communication with the reader.  His book offers many insights into the nature of ecological communities and why it is that they matter so deeply.  It is also further evidence if we need it of how profound the effects of anthropogenic global warming are set to be if we do not change our ways.