The God Species is an unusual book: a review of the environmental challenges ahead of us that manages to give a balanced and optimistic approach. In God Species he moves on from the general prediction of doom in Six Degrees to taking a look at what can be done. Some of his conclusions are surprising.

His approach is in terms of boundaries. These are limits that scientists have estimated we must not exceed in order to prevent ecological disaster (or, in fact, planetary catastrophe).

The first boundary is biodiversity. Mark Lynas says that the ‘Anthropocene’ (caused by man) Mass Extinction ‘and the death toll will soon rival that at the end of the Cretaceous, when the dinosaurs (and of the half the rest of life on earth) disappeared.’ The solution is to put a value on ecosystems as places of recreation, clean water and air and bring them into the marketplace.

Quite often Mark Lynas advocates using capitalism to solve our problems. As he says, preserving biodiversity makes economic and scientific sense. Once an animal becomes extinct the ecosystem to which it belonged falls apart – usually irretrievably. As well as having dire economic consequences to humans that depend on components of that ecosystem, unique resources are lost forever.

Climate Change is next on the list. In some ways the effect of global warming did not feel quite as catastrophic as in his previous book, although clearly it is something we need to urgently address. He points out that the release of methane hydrates from the ocean and the permafrost of Siberia is not thought to be imminent, for instance. However, his boundary for carbon dioxide concentration is revised downwards from 400ppm to 350ppm. Only with this concentration is the climate likely to stay similar to the one in which human civilisation developed and grew.

He says we cannot do this by reducing population (it would have to go down to just one billion) or reducing growth (because most people want and have a right to an improved standard of living). Instead it must be through reducing the carbon emitted by use of nuclear energy and renewables (solar, wind and HEP); and also research and development in these areas as well as cutting down on energy waste.

I found the chapter on the nitrogen boundary particularly interesting, despite the slight error at the beginning: elemental nitrogen has triple bonds not double. It described the importance of nitrogen fertiliser, and how this averted a Malthusian disaster at the beginning of the twentieth century. It, more than anything else, has allowed the population of the planet to grow, and so, in a way, is responsible for many of the other ecological problems today. Artificial fertiliser has led to direct problems as it is washed off the land and produces algae blooms in rivers and the sea. This growth deprives water of oxygen and it becomes a dead zone where nothing else grows. Overall the production of artificial nitrogen fertilisers should be reduced to 35 million tonnes a year from 100.

Mark Lynas lists some possible solutions: NOx boxes on car exhausts, maintenance of wetlands which foster denitrifying bacteria, removal of nitrogen compounds from sewage, avoiding excessive use of fertilizer, use of night soil, improving nitrogen uptake efficiency in crops using genetic engineering (convincing argument for this, and he is a recent convert), getting crops to become leguminous (i.e. fix nitrogen themselves using microbes).

The next boundary discussed is that of land use. It is important that land is kept in as close to natural state as possible, otherwise the biosphere is likely to collapse. No more than 15% should be converted to cropland to protect the earth system as a whole. He advocates city living as environmentally friendly as the wilderness areas are then left alone, and tends to decrease population growth. This ‘rewilding’of rural areas, he says, is already taking place.

In discussing the freshwater boundary he presents some surprising statistics. 60% of the world’s largest rivers have been fragmented by man-made structures such as dams, and two large dams a day for the last 50 years.

Freshwater is essential for human health and cleanliness and also agriculture. Damming water has provided water irrigation, but at the same time threatens biodiversity, changes local climate, and some rivers, such as the Yellow River in China are closed – with no water flow along some of its stretches at all. This may cause cities built on their deltas to sink. The limit to human consumption of water at 4,000 cubic kilometres a year has not yet been exceeded, but where this water is taken from is important. He recommends that unnecessary dams be removed and rivers serving ecological disaster areas such as the Aral Sea, are restored. This will mean cotton crops in arid regions are abandoned but they are unproductive anyway. Schemes such a China’s Three Gorges Dam present more of a conundrum since the ecological and social effects must be balanced against the advantages of a renewable source of electricity. Another surprising conclusion is that he advocates food is grown where water is more plentiful and transported. He is also in favour of water privatisation as a method of controlling water use, and necessary because public companies are not doing a good enough job.

The Toxics Boundary includes non-biodegradable plastics which are contaminating each part of the globe including the middle of the Arctic and the Pacific; hormones and molecules that have been found to effect marine and river life; and insecticides do not break down and are concentrated in the food chain, particularly in the Arctic. Chemicals already known to be toxic are already regulated. By 2018 new chemicals are to be tested and registered in the EU, with similar legislation in the US. Radiation toxicity is discounted because in areas where there is high natural radiation the cancer rates are no higher (except in areas where radon is emitted which increases the incidence of lung cancer). Effects of Chernobyl although devastating have turned out to be short-lived and less than feared. With the exodus of humans the ecosystems are flourishing. Listed against mine and oil refinery disasters the number of fatalities in the worst nuclear disasters are small. Dealing of waste is also manageable. He considers the Greens’ opposition to nuclear energy has been a big mistake, and may have contributed to global warming.

The colour of the sky is now more milky due to aerosols, and these form another boundary. The effect on global warming depends on the sort of aerosol particle and where it is. For instance a white cloud shielding the dark ocean will reflect more light and have a cooling effect, whereas a dark cloud over the poles will warm. Although the effect of aerosols is temporary it can have profound effects: for instance the brown cloud over India has diminished the Monsoon, and the smoke stacks of the northern hemisphere caused drought in Africa. Black carbon is mainly produced by developing countries, and is one of the easiest to address. Filters on diesel cars, scrubbers on ships, modernisation of coal-powered power stations in China and home stoves in India are the main solutions. In order to accomplish the latter he suggests the use of carbon-offset tariffs.

As far as sulphur-based aerosols are concerned he describes Nobel-prize winner Professor Crutzen’s idea to inject a2-4% of the 55 million tonnes that are produced each year into the upper atmosphere. These will reflect sunlight and yield a cooling effect which may temporarily ameliorate the effect of global warming. This is highly controversial. In the geological past, acidification of the oceans (another boundary) caused by increased vulcanism has caused mass extinctions. Although coral seems to have continued to flourish this is thought to be because of the neutralising effect of the the lower levels of the ocean. However, for this to happen there must be mixing, which requires over tens of thousands of years. Humans are producing carbon dioxide an order of magnitude more rapidly than the biggest super-volcanic eruption of the last billion years; the change may be too fast for the oceans to adapt and for life to evolve.

The boundary for the preservation of corals and marine life is in terms of the concentration of aragonite (the form of calcium carbonate used by corals to build shells) and this should not dip below 80% of pre-industrial levels. As long as the carbon dioxide level does not rise above 500ppm this should be okay. He argues against Matt Ridley’s assertions with regards to ocean acidification in The Rational Optimist, pointing out that a small change in pH is actually a large change in acidity because pH is a logarithmic scale.

He tells a very interesting and optimistic story about the hole in the ozone layer (the last boundary) and how politicians led the way in legislating for scientific and hence environmental change. This led to the banning of CFCs in the Montreal agreement of 1988 and consequently the hole in the ozone is now slowly recovering. However in Kyoto 1997 which hoped to do for climate change what the Montreal Protocol had done for the ozone layer there was failure because the USA refused to ratify and it also set the rich and poorer countries against each other. Mark Lynas was actually in the room when the Copenhagen treaty failed to agree targets in 2009, and his account is dramatic and depressing. China was flexing its muscles and establishing its new position in the world. Without China’s agreement nothing was possible. However, China is now leading the way in many respects post-Copenhagen. Although its emissions may be rising it leads the world in its investment in low carbon technology, and the US is losing ground.

There is a very interesting section discussing why the ‘libertarian right’ tend to oppose climate change arguments. It is, he believes, because they are forced to ‘confront the necessity of of respecting planetary limits’. He is equally dismissive of Green ‘dead-end ideology’ which advocates the adoption of a wartime rationing to combat climate change. He says that both camps tend to ignore scientific evidence to make their case. He believes that we can keep within the boundary limits even with economic growth, and thinks it is only fair that developing countries achieve the same standards of living as people in the west. He envisages a world economy that enjoys constant growth with lower material use if we recycle and use sustainable energy.

I was cheered by reading this book because it makes change seem possible. As he says, the pessimistic approach seldom works, and he is honest in that he admits to have completely revised his opinions on nuclear energy and genetic engineering. I am not sure I agree with everything he says, but it has made me think and consider things in a different light. As Mark Lynas says: The truth is global environmental problems are soluble. Let us go forward and solve them.’ It is a worthwhile book, very well written, bringing together much peer-reviewed scientific information, so that the general reader is brought quickly to speed. I recommend it to anyone interested in a hopeful viewpoint on ‘how the planet can survive the age of humans’.

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Review by Clare Dudman (originally on her blog)