Manaus: What will happen to the Amazon as the climate changes? This is one of the key questions troubling climate scientists and the policymakers charged with responding to their predictions. The picture painted by most climate models doesn’t look good – some suggest that the vital ‘Lungs of the Planet’ will be semi-arid desert by the end of the century; others that its efficiency at mopping up carbon dioxide will be drastically reduced and so too its biodiversity.
The Amazon is extraordinarily biodiverse. This vast swathe of green that’s visible from Space holds an unrivalled number of species, some of which remain unknown to science. “We know next to nothing about the Amazon – not even the mammals, not even the primates, are known yet,” says Adalberto Luis Val, the director of INPA (the National Institute for Amazonian Research) in Manaus. “Two years ago, we visited a place not far from here and discovered a new species of monkey. And we are finding countless new species of insects and spiders,” he says.
If the analysis of the climate models are right, taxonomists are in a race against climate extinctions to find and name new species. Even if the species we know about do not become extinct, they may change dramatically under the pressures of climate change, Adalberto says. The trouble is, our knowledge of what changes will happen is based on computer simulations, on the palaeo record and on the few recorded occurrences of climate change already effecting – usually bird – species. We can’t, in other words, see into the future.
If we can’t go into the future, Adalberto is about to bring the future to us (albeit in a small, controllable way). In the first experiment its kind, he is taking a peek at the Amazonia of the coming decades, taking the three IPCC scenarios (B1, A1B, A2) as his guide, plus a control.
Adalberto is a fish biologists, so he’s understandably beginning the experiment with fish – everyone wants to know their loved ones will have a safe future. We visit the fish research labs at INPA, which has the most delightful jungly campus of any research institution I’ve visited – the aquatic mammals research centre, for example, features charismatic Amazonian giant otters and adult and baby manatees rescued from encounters with fishing nets.
The fish department has everything from pirañas to oscars, a type of cichlid. To my mind, oscars are rather ordinary creatures, but Nick, who used to keep Amazonian fish in a tank, goes gaga over them and gets into a prolonged geeky conversation about the various types. And the researchers convince me that the oscar is rather special. For one thing, it is able to shut down its metabolism, going into a type of hibernation, without a drop in temperature. It needs to do this because the ‘black’ river in which it lives becomes massively depleted in oxygen (and high in dissolved carbon dioxide) during the night (photosynthesisers can’t work at night, so everyone’s respiring).
This is an unusual situation for a creature to find itself in. Many ‘black river’ fish breathe air at the surface, so don’t face the problem. The only other complex animals that deal with oxygen deficiencies live at high-altitude and adapt by physical changes such as an enlarged heart, for example (or a heart that metabolises lipids and glucose, rather than just lipids, so as to make more ATP). But the oscar copes with almost no oxygen in an entirely different way. First, it shuts down aerobic metabolism, switching to anaerobic, just as we do. And it reorganises its blood flow to different tissues, dumping build-up of lactic acid in those that can tolerate it, such as white muscle, but not the heart of liver. Most fish would die if they didn’t flush out their lactic acid. And then, at some point, a biological trigger that the researchers are still looking for, causes the oscar to flip from anaerobic metabolism to a kind of hibernation for the night.
“It looks dead, it plays dead, it pretty much is dead until the next day,” says Maria Tereza Fernandez Piedade, who’s leading the oscar research programme.
The oscar, which lives in this hypoxic environment, is also remarkably well adapted to waters with a high organic carbon content – waters that are pretty acidic (around pH 3.5). How it retains its ions (sodium, potassium, calcium, etc) and manages to uptake ions from its nutrient-poor environment is another wonder of adaptation involving specific enzymes.
These unusual qualities make the oscar a superb choice for Adalberto’s experiment, which will look at changes in carbon dioxide levels, temperature and humidity.
He’s chosen 10 Amazonian river fish species, a host of aquatic insects, microorganisms and flora, and he is creating four identical 9-cubic-metre micro-cosmoses, three under the CO2, temperature and humidity constraints of the IPCC scenarios, and one as a control. The micro cosmoses will be left for at least a year, before results are analysed.
We visit the construction, complete with sealed double doors, a clean room, Advanced high-throughput genetic sequencer to look at genetic alternations caused by the ‘climate change’, and a computer-controlled complicated air system all backed up by an independent generator. The experiment will be switched on next month.
What do you expect to happen? “Some fish may die, others will probably over-express or down regulate certain genes linked to temperature , CO2 and pH adaption, like the hypocapnea genes,” Adalberto says. “We don’t know for certain, and that’s the whole point.” He reminds me that the last time there was a massive increase in atmospheric carbon dioxide, it was accompanied by an explosion in numbers of fish species. But that occurred over a far longer timescale than the current rise in CO2.
“The Amazonian fish are adapted to high temperatures, but extremely sensitive to fluctuations in those temperatures,” he says, explaining his prediction of ‘extinctions’ in the experiment.
The Amazon is much more than the sum of its parts, of course, and although I’d never say it to Adalberto, fish might not be the most crucial element of the forest. They are an indicator though. And this is just the beginning – the experiment will be enhanced to include a bigger ecosystem, including mosquitoes (some of which will carry the malarial and dengue parasites), mammals and, one day, trees. Adalberto is also designing an in-the-field version which raises temperature along a river at various sections and looks at what happens.
A few other micro cosmoses exist in labs around the world, but none is looking at this particular ecosystem of global importance. It begs the question: why wasn’t this done 30 years ago?
Wandering Gaia 
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