Cities across the world are increasingly at risk from climate change. People living in extreme poverty are especially vulnerable, both because global warming will tend to hit developing countries the hardest, and because they have less money to throw at the problem.

We used newly-available data to investigate how cities are responding to climate change and whether resources are being allocated efficiently or fairly. We expected there to be differences in spending between rich and poor. But we did not expect them to be so vast, with New York for instance spending more than £190 (US$260) per person to protect its people and infrastructure from the impact of climate change, while Ethiopia’s capital Addis Ababa spends less than £5 ($7).

It seems the amount spent on climate adaptation is driven more by the amount of wealth at risk rather than the number of vulnerable people.

Adaptation simply means any actions that anticipate the negative consequences of climate change—to human health, the economy or ecosystems—and attempt to minimize the damage. In big cities this might mean raising sea walls to tackle sea level rise or expanding drains to cope with bigger storm surges.

We need a comprehensive picture of how much is being spent on these adaptation measures across the world. The Millennium Development Goals, despite their shortcomings, have demonstrated that measuring a problem provides an invaluable baseline from which improvements can occur.

For this study, published in Nature Climate Change, we focused on spending in ten megacities. New adaptation spending figures were gathered and analysed using data triangulation, which draws on many different sources and types of data to arrive at more accurate estimates. Our work on this is part of a wider project on measuring the size of the green economy.

Where ever you look, this “adaptation economy” remains a small part of the overall economy—a maximum of 0.33% of a city’s gross domestic product. Yet there are real disparities between cities. As you might expect, developed cities spend significantly more per capita. After all, most things cost a lot more in the US than in Ethiopia, and new drainage systems, air conditioning and so on are no different.

Georgeson et al/Nature Comms, Author provided Cities in richer countries spend more in total and per head (2014-15 data). Paris is an exception due to narrow definitions of its ‘city proper’.

But this same disparity also applies as a percentage of city GDP. The three rich cities we looked at spend nearly half as much again as the developing cities (around 0.22% of city GDP, compared to 0.15%), even though climate change is a far scarier prospect for low-lying, flood-prone Jakarta or already-hot Addis Ababa than it is for London or Paris.

Of course, cities in poorer countries have greater competing needs for their finances. Things Londoners or Parisians can take for granted such as clean water or basic healthcare are still pressing issues in Lagos or Mumbai.

Yet such disparity still has to end, particularly as between now and 2050 the major growth in urban populations will be in China, India, Indonesia and Nigeria. In these countries we need to think about how to boost cities’ resilience through far more adaptation funding.

Georgeson et al / Nature Comms, Author provided Beijing tops the charts for adaptation as a percentage of GDP (2014/15 data).

It can be done. Just look at Beijing, which stands out because the proportion of its economy devoted to climate adaptation was significantly higher than any other city in the study. Almost half of this was spent on changes to the built environment such as water efficiency retrofitting—a much higher ratio than any other city—with less going towards health or agriculture.

The fact the Chinese capital is taking adaptation seriously is linked to strong central government policies, which encourage cities to face up to climate change. In China, all provinces have a comprehensive adaptation plan and a taskforce to deliver it. When governments offer leadership and policy certainty, things will happen.

Most cities at least show solid growth in adaptation spending over the past five years, beyond their average GDP growth for the period. But adaptation spending was more volatile in Addis Ababa and Lagos, the cities in the study that spent the least in real, proportional and per capita terms, and heavily-dependent on a few specific projects. This should be a cause for concern.

It is clear that insufficient funds are being spent to protect major population centres in developing and emerging economies. Our study is an early warning sign: we must remain focused on protecting people at risk, and not just the “capital”.

This post originally appeared at The Conversation. Follow @US_conversation on Twitter.