The first law of economists states that for every economist there exists an equal and opposite economist. In that spirit, Nature this week presents related articles that take contradictory stances on what the banking system could, or indeed should, learn from ecologists. In a Perspective (see page 351), Andrew Haldane, executive director of financial stability at the Bank of England in London, and Robert May, a theoretical ecologist at the University of Oxford, UK, and former chief scientific adviser to the UK government, argue that the stability of complex networks of linked dependencies that make up the world's financial system can be tested using a simplified ecological model. They say that the results of their approach highlight ways in which economic policy could be changed to make the system more secure. Regulation of elements such as liquidity ratios, banking structures and trade in complex derivatives, they say, should work to protect the system rather than individual banks.

In a News & Views Forum (see page 302), this approach is criticized as potentially dangerous by Neil Johnson, a physicist at the University of Miami in Florida who studies real-world complex systems. Johnson says that policy implications drawn from such a simplistic model will be unreliable, because they will depend so heavily on the assumptions used to prepare the model. But Thomas Lux, an economist at the University of Kiel in Germany, offers a more supportive view. He says that the similarities between financial markets and ecology are real and relevant. For example, the 2008 default of the Lehman Brothers financial services firm had contagious effects similar to those of a 'super-spreader' of disease. Researchers should go beyond Haldane and May's simple model, says Lux, and build in factors such as interbank credit lines.

Given such contrasting views, how seriously should policy-makers take lessons from nature when it comes to financial regulation? Using natural models to set policy has proven difficult, even for ecological policy. Witness the controversy that has surrounded the UK government's handling of foot-and-mouth outbreaks and whether to tackle bovine tuberculosis by culling badgers, which can spread the disease. In other areas, such as conservation and fisheries, research offers more clear-cut recommendations. But in such cases there is often a failure of political will to follow through. Which is the case in finance policy? Perhaps the best approach is to keep a cautiously open mind — or to remember that the second law of economists states that both the economists cited in the first law are wrong.

Wider discussion of the ideas raised by Haldane and May will inevitably throw up many questions. Among them, we expect, will be: why is Nature publishing research in economics? As a natural-sciences journal, most of economics falls outside our primary-research remit, and there are some fundamental differences in approach between the fields. For example, in financial systems, as Haldane and May point out, evolutionary forces often act for the survival of the fattest, rather than the fittest. But in this case, we think the clear links that the authors draw with ecology will make their study of interest to readers. More generally, we are happy to publish primary economic research that has significant scientific implications, for example in fields such as behaviour, conservation biology, systems biology or physics. With such an approach, perhaps both economic science and natural science can benefit.