Plans are forging ahead for wind farms in U.S. waters with the first likely to be a 130-turbine farm in Nantucket Sound. As in many countries, the U.S. path to offshore windpower has not been without controversy. Critics contend that wind farms are bad for wildlife, such as birds that fly into the turbines. However, the evidence from Holland, where offshore wind farms have been in use since 2006, points the other way.3 Turbine footings created new habitat for creatures like mussels, anemones, and hydroids, and shelter for schools of fish. Since the Dutch farm was put off-limits to fishing, it may in time come to act as a protected area of sorts. While some birds avoided the farm, like common scoters and gannets, others were attracted, like the great cormorant. Harbor porpoises were heard calling more often within the wind farm than outside, perhaps because they could find more to eat there. The potential for offshore wind energy has also been recognized in China with the first farm completed in 2009. Developers there have plans for many more, given the great length of the Chinese coast. This move into clean energy is welcome for a country that has relied so heavily on coal up to now.
Waves and tides afford other possibilities for power generation whose potential has barely been touched. Two notable exceptions are a hydropower barrage across the Rance estuary in France, which has been in use since 1966, and a tidal turbine at the mouth of Strangford Lough in Northern Ireland, which has two fifty-foot diameter blades. Tidal dams have existed since at least the Middle Ages, when they were used to power coastal corn mills. But our capacity to take advantage of tidal power has grown beyond the wildest dreams of the monks and millers of long ago. Today plans have been drafted for colossal schemes like the Severn Barrage in southwest England. At its most ambitious, this scheme would bridge eleven miles of the Severn Estuary which has, at forty-nine feet, the second greatest tidal range in the world. It could supply over 10 percent of the UK’s electricity needs in 2020, but comes with a large environmental price tag. Like dams further upstream, barrages change water levels. Tidal range would be reduced and the area of rich salt marsh and mudflat habitats vital to hundreds of thousands of migratory birds and commercial fish would fall. So far, the environmental costs of the Severn Barrage have been perceived as too high and the project was shelved (again) in 2010 while eight new nuclear power stations were given the go-ahead. But as the costs of climate change become clearer, resistance to tidal barrages may wash away. The pace already seems to be picking up. There has been a small tidal generator in Canada’s Bay of Fundy since 1984, and in 2006 a demonstration project was installed at Race Rocks in Vancouver Island. South Korea has several tidal power stations and ambitious plans for more, while China has installed one scheme and the first Indian station is planned for 2013.
Wave power schemes are more palatable to conservationists. To stand at the edge of a cliff, stiff to the wind and watch the waves hurl themselves ashore, and feel them rumble through your body is to know the power of the sea. The immensity of the energy is palpable. But many engineering challenges must be overcome before waves will be viable competitors to wind and tide. Many ways have been devised to harness their power. In one, waves rise and fall in an air-filled tube to push air through a turbine. Another involves flexible floating sausage strings whose bending pressurizes hydraulic fluid to drive motors that feed a generator. There are several prototypes off the European coast, one named Pelamis, after the seasnake (a better name than “sausage”). A third method relies on waves breaking over a wall to fill a reservoir which then drains through a turbine. None of these methods is commercially attractive as yet.
Generators might also tap the power of strong currents to turn underwater rotors, following the principle of tidal barrages. The mighty Gulf Stream, as it pours through the narrows between Florida and the Bahamas, might be an ideal location, or the Kuroshio Current as it races past Japan. Such generators would have to be moored in deep water, probably one hundred feet or more below the surface, to avoid causing a shipping hazard. To date, none have been built.
Progress toward restraining emissions to keep them below the target of 450 parts per million of atmospheric carbon dioxide has been desperately slow. As of 2011, emissions were rising in line with the worst case scenario of the IPCC. With every failed negotiation the likelihood rises that we will overshoot. An increasingly vocal group of scientists has begun to think the unthinkable. If we can alter the planetary climate by filling the atmosphere with carbon dioxide, perhaps we can find another way to dial down the heat. Some are now looking for ways of removing carbon dioxide from the atmosphere or finding methods to cool the planet. Such “technofixes” remain highly controversial, and there is a real risk that tinkering with the planetary thermostat could do more harm than good. Ken Caldeira, the American scientist who was among the first to point out the risks of ocean acidification, put it well in his testimony to a British Parliamentary Committee in 2008:
Only fools find joy in the prospect of climate engineering. It’s foolish to think that the risk of significant climate damage can be denied or wished away. Perhaps we can depend on the transcendent human capacity for self-sacrifice when faced with unprecedented shared, long-term risk, and therefore can depend on future reductions in greenhouse gas emissions. But just in case, we’d better have a plan.4
Carbon dioxide levels may already be too high for the most sensitive habitats on Earth and the most delicately balanced parts of the world’s climate system. I keep coming back to coral reefs. They have suffered badly from global change already and their very survival is now in doubt because of the one-two punch of warming and acidification. In the summer of 2009 I spent a day with a distinguished group of experts to talk about what we can do to save coral reefs. Late on a sunny London afternoon, David Attenborough and the Australian scientist Charlie Veron presented our conclusions. They told the waiting press that coral reefs as we know and love them are probably doomed unless we can reduce carbon dioxide levels to less than 350 parts per million—about 10 percent less than where we are now and 100 parts per million less than target levels negotiated for unsuccessfully in Copenhagen in 2010. If these magnificent habitats are to survive, we will have to find a way to suck some of the carbon dioxide we have already released out of the atmosphere.5 Our only hope is carbon sequestration.
There is no shortage of ideas of how to dial back our carbon footprint, some madcap, others serious. Every meeting I go to these days seems to attract a collection of entrepreneurs touting their schemes for climate geoengineering. Glossy brochures are handed out, breathless talks given, and promotional videos screened. There is a smell of money in the air, and these people are in hot pursuit of cash from carbon sequestration. At the moment they are pursuing money from companies who want to offset their carbon footprint, but government cash may follow in the future if binding emissions targets are negotiated. It is hard to fault their enthusiasm, but most of these schemes seem to have been poorly thought through. Engineering fantasy often seems to trump common sense and suppress the desire to test whether the machinery on offer can possibly live up to the hype, or whether it is even sensible to use it in the first place.
One company plans to break down the two-layered structure of our tropical oceans where warm, low nutrient water floats on top of cooler, nutrient rich water below. Their idea is to speed up carbon dioxide removal by getting nutrients back to the surface, where there is more light, to stimulate plankton growth. Their scheme would deploy vertical pumps powered by waves to suck water from a few hundred meters down and release it near the surface. To make a difference you would have to seed the oceans with millions of these pumps (remember, there are $$ in their eyes). As the company rightly points out, global warming will increase the stability of these ocean layers by heating the surface more. Their plan, they explain, could help to feed the world, since more productive oceans produce more fish. The problem is most of the carbon taken up under this scheme would simply be released again when the plankton and fish in the surface waters died. In most places only a tiny
fraction of the extra production would be taken out of circulation for the long term. The effect would probably be piffling. Producing electricity from their wave generators might be a more reliable means of reducing carbon emissions. The company believes that their pumps could be used to stir up dead zones, or cool coral reefs threatened by bleaching. Since hurricanes form in places with high sea temperatures and are sustained by drawing heat from the sea, they have also suggested that their upwelling pumps could reduce the frequency and intensity of tropical cyclones. Their entrepreneurial fire burns bright.
Other means of making the oceans more fertile and productive have been proposed. Far from coasts, enormous swathes of the sea are not short of the nutrients that usually limit plankton growth—nitrogen and phosphorus—but they have very low productivity nonetheless. Their problem is a lack of the micronutrients that are needed in trace quantities to create the building blocks of life. Iron is one essential micronutrient, whose value to life was established billions of years ago in iron-rich water as metabolic pathways evolved. Mostly the sea gets its iron from river runoff or windblown dust, like the red dirt that blasts from the Sahara across the North Atlantic. Places like the southeastern Pacific and mid-Indian oceans are short of other nutrients essential for life, but about a quarter of the oceans are limited by iron alone. The whole of the Southern Ocean around Antarctica is chock full of nitrogen and phosphorus but far from any source of iron.6 Likewise, the tropical eastern Pacific has plenty of nutrients but little iron. Perhaps, some have speculated, plankton production could be given a push if iron were added.
One of the first to notice the link between plankton growth, iron, and climate was the U.S. oceanographer John Martin, from Moss Landing Marine Labs in California.7 In the late 1980s he noticed an inverse relationship between the amount of iron in deep-sea sediment layers and the amount of carbon dioxide in the atmosphere at the time those sediments settled to the seabed. Periods of low atmospheric carbon dioxide corresponded to ice ages while higher levels were present in the mild periods between glacials. Martin thought that iron was the key to low carbon dioxide levels, because it boosted plankton growth that pulled carbon from the atmosphere. The bodies of dead plankton and fish carried some of that carbon to the deep sea. In an experiment in the tropical eastern Pacific in 1993, Martin proved that a soluble iron compound mixed into the sea could trigger a plankton bloom. In the flush of enthusiasm that follows success in science, Martin made a quip that became famous: “Give me half a tanker of iron, and I’ll give you an ice age.” Luckily not!
Entrepreneurs and other freelance enthusiasts have since taken a leap of the imagination and proposed that ocean fertilization on a massive scale could rid the atmosphere of excess carbon dioxide. A niggling flaw in their plans is that nobody is sure where carbon dioxide absorbed by plankton will end up. Indeed, many scientists now believe that the great majority of extra carbon dioxide absorbed will simply be rereleased into surface waters as the plants and animals decompose. Surface waters are pretty good at recycling nutrients through microbial action before they sink to depths beyond the reach of mixing by winter storms. How deep that is varies from place to place and depends on the violence of winter weather and vigor of local currents, but in most places it is somewhere between three hundred and three thousand feet. Until carbon gets beyond this mixing zone, it hasn’t really been taken out of the atmospheric system.
As of now, there have been twelve attempts to fertilize the sea with iron. Most caused a pleasing spike in phytoplankton growth but offered little evidence of carbon export to the deep sea. Early on, several companies set up shop and began to pull in venture capital money on the grounds that they could sell “carbon offsets” from artificial ocean fertilization. One company, Planktos, even got around to doing its own fertilization off Hawaii, dumping a paint-based iron compound into the sea along a thirty-mile track from the rock star Neil Young’s antique yacht. While Young might have been pleased to have offset his massive carbon footprint, the findings of this “experiment” were never made public.
The idea of dumping iron to offset our carbon consumption is highly questionable, since fertilization contravenes the terms of the London Dumping Convention. In recent years two United Nations Conventions (on biodiversity and marine pollution) have come out against ocean fertilization. Planktos folded in 2008, and its founder bitterly attacked environmentalists for what he saw as a hate campaign. There are still others in the game, such as Climos and the Ocean Nourishment Corporation (who propose to fertilize with urea as a nitrogen source in areas not limited by iron), but enthusiasm for this approach is fading. Projections suggest that even the most optimistic scenarios could only increase ocean uptake of carbon dioxide by about a ninth of present emissions. It turns out that John Martin’s half tanker of iron was way off the mark. To trigger an ice age you would have to continuously fertilize the entire Southern Ocean, all eight million square miles of it. If you stopped that fertilization, things would swiftly bounce back to where they were.
Another possible downside of fertilization is the effect on deep water oxygen. As I have already explained, when dead plankton sinks beneath the mixed surface layer of the sea it falls into a world where oxygen is scarce. Rotting plankton will use up precious oxygen and could enlarge the area of the ocean where there is too little to sustain anything but the simplest life-forms.
A different approach to tackling our climate problem is to extract carbon dioxide from the atmosphere and pump it into the deep sea. Below about ten thousand feet deep the high pressure and low temperatures turn carbon dioxide into a liquid denser than seawater. The idea is to inject liquid carbon dioxide through long pipes into ocean trenches or pool it on the seabed. While these ultradeep trenches would conveniently hold lakes of carbon dioxide, each sustains its own distinctive community of life, with many species found nowhere else, and it would likely cause extinctions. Experiments with small puddles of carbon dioxide placed on the deep-sea bed off the California coast suggest that the approach is feasible, but again this solution has fallen foul of environmentalists. Video footage of puddles show fish swimming nearby apparently unharmed, but capping large areas of ocean sediments with liquid carbon dioxide would certainly kill most of the animals that live there. There are also concerns that carbon dioxide stored in this state would find its way back to the atmosphere. Calculations suggest that only about 6 percent would mix back into the water over two hundred years (though up to 20 percent more would return later), but the technique would still buy us precious time to reduce emissions. It would, however, enhance the problem of acidification in the deep sea, so this idea is not very popular either.
A more realistic and practical solution to carbon dioxide disposal can perhaps be found in active or spent oil wells. One Norwegian oil company has extracted carbon dioxide from natural gas and pumped it back into wells below the North Sea since 1996.8 The method was introduced to reduce emissions taxes and transport expenses and to increase yields from the well rather than to reduce emissions of a greenhouse gas. This concept, known as carbon capture and storage, has become a cornerstone of the much vaunted “clean coal” technology recently proposed for the next generation of power stations. There is little chance that we will abandon fossil fuels in time to avoid serious climate change, so we urgently need to find ways to generate power at less cost to the natural environment. There are several ways to capture carbon dioxide at the point of emission. The gas can then be pressurized, piped as a liquid, and forced back underground. Active or spent oil and gas fields seem to offer a means to lock away carbon dioxide for thousands to millions of years. Water from salty aquifers deep beneath the Earth’s surface could also be displaced by carbon dioxide (the excess water would leak back into the sea). Such carbon capture and storage is now a central plank of international negotiations to avoid climate change. It could save up to 20 percent in emissions.9 Unfortunately, current underinvestment in the technologies required means we will probably overshoot emissions ta
rgets and so risk dangerous climate change.
There are still other ways in which the oceans can help us engineer a cooler climate that remain the stuff of daydreams. One idea is to enhance the weathering of silicate rocks by exposing ground-up rock to hot carbon dioxide and water, and either storing the reaction products as solid rock or dispersing it throughout the oceans. Silicates make up most of the rock in the Earth’s crust and include sand, clays, quartz, olivine, and diatomaceous earth, a substance made of the ancient remains of planktonic diatoms whose shells were built of silicon. Of these, olivine is especially suitable. Ocean dispersal of the carbonate reaction product has the advantage that more carbon dioxide is used up, and it could help reduce acidification because of the bicarbonate produced when it dissolves. The huge expense and disruptive impacts of mining the silicate rocks is a potential killer, regardless of any scruples about possible harmful effects on marine life.
The Ocean of Life Page 30
