Do you care more about the state of the environment than about world poverty? If you had only one return ticket, would you send Michael Meacher, the environment minister, or Clare Short, the development secretary, to the World Summit on Sustainable Development in Johannesburg, starting on 26 August?
And just what is this summit, attracting more than 20,000 well-fed and well-shod delegates, plus 40,000 hangers-on, into a region devastated by Aids and drought, actually about? Is it, as Clare Short claims, a development summit aimed at saving humanity from poverty? Or is it, as the essential presence of Michael Meacher and planeloads of environmentalists would suggest, an environment summit, aimed at saving nature from humanity?
Well, it's both. The World Summit on Sustainable Development, the mega-summit that could quite literally end all mega-summits, is the culmination of a new theory sweeping charities, national governments, the UN, and at least the press releases of the World Bank: fighting poverty and saving the environment are in fact the same battle.
The Johannesburg summit is semi-officially "Rio + 10", a reference to the Rio Earth Summit of 1992, which was almost totally dedicated to saving nature, with a few decorative (and subsequently broken) promises about relieving poverty attached. But a lot happens in ten years. This time, the summit is about how we can reduce poverty and save nature at the same time.
The theory is not just that it is desirable to do both at the same time - only George W Bush could disagree - but rather that you have to do both at the same time, that you can't do one without the other. It turns the old theory of trade-offs between development and the environment on its head; they are now part of the same bargain. For environmentalists, roads being cut into forests used to be part of the problem; now it can be part of the solution.
"You can't tackle poverty without tackling environment, and you can't tackle environment without tackling poverty," says Andrew Lee, policy director at WWF (World Wildlife Fund), the former save-the-panda charity. WWF has just entered a permanent strategic partnership with the aid group Care International, and is already working on various projects with Oxfam. Friends of the Earth has been in deep policy discussions with the World Development Movement. Even the IUCN, also known as the World Conservation Union, the UN body that is responsible for protecting endangered species, has started addressing development issues and, with particular reference to bushmeat, refers to "the sustainable use of wild species for meat".
Development and environment charities started working together in the run-up to the Johannesburg summit, and soon realised that they have so much in common, they should just lobby and co-ordinate their responses, speaking with one voice - the Eco-Equity Coalition, which includes Oxfam, Friends of the Earth, WWF, Care International, Greenpeace and others. "It's worked quite well. I haven't seen any major policies that we've got major differences on," says Antonio Hill, policy adviser for environment, markets and sustainable livelihoods at Oxfam.
The new theory is morally satisfying - you no longer have to choose between saving people and saving plants. Environment groups are no longer open to the accusation that they are anti-people, and aid groups are no longer open to the accusation that they are anti-nature. It is a theory that takes the scramble for the moral high ground to its logical conclusion.
But it is also based in harsh reality: the old, neocolonialist, European approach of telling poor people in poor countries to stop devastating their environment simply does not work. "We've moved on," says Lee, "from thinking you can put fences around places to protect them. We've realised that the only way to work sustainably is to work with people. Unless you start from where people are, and their need for a livelihood, you get nowhere."
WWF and other conservation groups have stopped simply trying to keep people out - and are trying instead to get them involved. If people depend on something to make a living, the argument runs, they will make sure it is conserved.
The Kisongo Masai of southern Kenya used to hunt wildlife such as lions to show off their prowess. Because the money from ecotourism all went to the government (or, more precisely, to ministers), they didn't care that the numbers of wild animals were dwindling. Now, one project gives them stewardship of the animals in return for a share of ecotourist profits. In Brazil, the Southern Bahia Agro-ecological Movement gets away from conservation as simply locking out the landless poor, and helps develop sustainable agriculture within the forest so they have an interest in keeping the forest alive.
Illegal logging by large corporations has been a key area of co-operation between green groups and aid groups: it not only destroys the forest, but deprives the people who live in the forest and their governments of an income. Both sides share an aim of ensuring that wood is logged sustainably, so that the people can make a living from protecting the forest.
Bushmeat campaigners have also learnt you cannot tackle one thing without the other. The people are eating the animals of the African jungle almost to extinction, but if conservationists just tell them not to eat the animals, they are in effect telling them to starve. Instead, they now help the people who live in the forest develop new methods of agriculture so they can feed themselves.
The co-operation extends to all major issues. Global warming not only damages the fragile ecosystems of the earth, it also leads to droughts and reduces harvests: green groups and aid groups alike want to tackle it. Both want to ensure that trade policies not only target the poor, but do not damage the environment, which poor people tend to depend on. Both want to ensure "corporate responsibility", so that companies pay the same regard to how they treat people and the environment in the developing world as they do in the developed world.
The old theory was that, up to certain income levels, environmental degradation was just an inevitable part of development. Poor people pollute more because they have more urgent priorities than conservation; only the rich can afford to conserve parts of their land, and can afford the clean technologies that reduce pollution. But Barry Coates, director of the World Development Movement, insists this is just not true: "The new research is that bad environmental practice produces costs, whatever the stage of development."
The governments of the developing world seem increasingly to agree that development and environment are one agenda: China is making huge strides in cutting air pollution from factories; Brazil has declared one-tenth of its land area as officially protected.
But it is not clear how much the British government agrees. The Department for International Development talks about "sustainable livelihoods", but Clare Short has suggested that environmentalists are barriers to development. She has made it quite clear that she thinks the Johannesburg summit is about development, not the environment, and that the two don't go hand in glove.
"It's disappointing," says Tony Juniper, director designate of Friends of the Earth, "that people like Clare Short see it as a trade-off. There are still pockets of resistance to this working together." Even the World Bank, he says, has seen the light. But many businesses cling to the "trade-off" theory, because they fear that increasing environmentalism could damage their interests. "A lot of corporations have a vested interest in this divide. The fossil fuels and motor industries see [bridging] it as a direct threat to their business."
But do Short and big business perhaps have a point? Although it may be easy to see the convergence of interests between green groups and aid groups in straight conservation issues such as bushmeat, or big issues such as global warming, it is not obvious on the issues that are top of the agenda at Johannesburg. One of those issues - ensuring that everyone has access to electricity - could easily end up increasing global warming. Another - creating universal access to safe water and sanitation - could damage river ecosystems, or even drain them dry.
The charities have answers. "We're in favour of small-scale local distributive power and renewable energy," says Kevan Bundell, senior policy officer at Christian Aid. "It's about how we make efficient use of the water, rather than just trying to find new supplies from rivers or boreholes," says Juniper.
But many in government are sceptical that the solutions are so neat. There are other areas, too, where there are clearly trade-offs. In parts of Africa, the elephant population outside national parks is increasingly coming into conflict with the burgeoning human population. Juniper - the high priest of convergence - thinks that to make this an issue is to miss the big picture. "Elephants," he says, "are not going to go extinct because they are culled outside wildlife parks, nor is Africa going to starve because of elephants trampling crops. However, both are threatened by climate change."
Another contentious area is "food miles" - should we fly in all our green beans from Kenya? The Greens say no, because flying damages the environment; the aid groups say yes, because it creates jobs and prosperity in poor regions. The topic causes heated debate in both camps.
Such disputes are unlikely to stop the pace of convergence, which is transforming the way charities work. Friends of the Earth now operates in 70 countries, most of them in the developing world. "We're not a European, white-middle-class-dominated movement," says Juniper. "On trade, our Latin American and South Asian partners are very radical."
But how far can it go? As well as the WWF-Care International link, groups such as the World Foundation for Environment and Development in the US have been set up specifically to deal with both issues at once. Friends of the Earth is refocusing itself as a green group with a development agenda, confident that its members will support its change of direction - a large number are already members of Oxfam.
Could it go further? Some years ago, there was brief talk of WWF merging with Oxfam, and it seems likely that such mergers will come back on to the agenda.
"That will come in the next five years, for sure. It would make sense," said one senior official in the field.
Charities that value their own separate identity may resist, but it would make it easier for their supporters. You would no longer have to decide whether you care more about poverty or the environment. You can support both at once.
Anthony Browne is environment editor of the Times