By Richard Black
Environment correspondent, BBC News website
Have China's population curbs helped the global environment
As the UN climate summit in Copenhagen approaches, exhortations that "we must get a deal" and warnings that climate change is "the greatest challenge we face as a species" are to be heard in virtually every political forum.
But if you look back to the latest definitive check on the planet's environmental health - the Global Environment Outlook (Geo-4), published by the UN two years ago - what emerges is a picture of decline that goes way, way beyond climate change.
Species are going extinct at perhaps 1,000 times the normal rate, as key habitats such as forests, wetlands and coral reefs are plundered for human infrastructure.
Aquifers are being drained and fisheries exploited at unsustainable speed. Soils are becoming saline, air quality is a huge cause of illness and premature death; the human population is bigger than our one Earth can currently sustain.
So why, you might ask, are the world's political leaders not lamenting this big picture as loudly and as often as the climate component of it?
Has climate change hijacked the wider environmental agenda? If so, why? And does it matter?
These are questions I've been able to put to a number of leading environmental thinkers for a BBC Radio Four documentary, Climate Hijack.
Mike Hulme, who led the influential UK Tyndall Centre for Climate Change Research until recently, believes the climate issue is rather enticing for the modern leader.
"The characteristics of climate change are quite convenient for politicians to use and to deploy both at a popular level but also at a political level," he says.
He argues that climate change is seductive to politicians because it is a long-term issue - so decisive action is always posited for some time in the future, at a time that can always be made yet more distant - and someone else can always be blamed.
So Europeans used to blame the US, the US would blame China and India, and developing countries would blame the entire developed West.
"It's very easy to pass responsibility for failure somewhere else
and in the process of doing that, one is able to keep one's own credibility and record, with the appearance of being much more progressive and constructive."
According to this analysis - and in contradiction to Al Gore's famous phrase - climate change has acquired its huge profile largely because it is a far more convenient truth than poor air quality or biodiversity loss or fisheries decline, where the actions needed are more likely to be national or local - and certainly more convenient than tackling the issues that underpin everything else, the size of the human population and our unsustainable consumption of the Earth's resources.
"I don't think it's a competition, actually," says UK Environment Secretary Hilary Benn.
"We're coming to see that we've got a bit of a problem and we've got to live within the Earth's means."
In an ideal world, he would surely be right - all of these issues would receive the appropriate amount of political time and action.
But as far as the UK is concerned, there is a widespread feeling among environment groups - hard to quantify, and not always something they are willing to say on the record - that the government is only really interested in climate change.
And some say the balance has been tipped further by the creation of the new Department of Energy and Climate Change (Decc) under Ed Miliband, which removed most climate responsibilities from Defra.
The head of one large UK environment group told me last year: "If we want to talk about climate change, we can get a meeting with the prime minister. If we want to talk about biodiversity, we can't even get a meeting with the environment secretary."
This is a picture that Hilary Benn rejects; he says his department's doors are very much open to people bringing concerns about biodiversity, or about any other issue within his remit.
Nevertheless: "Climate change is at the forefront of most politicians' minds who are concerned about the environment," says Graham Wynne, chief executive of the Royal Society for the Protection of Birds (RSPB), probably the UK's most influential conservation group.
"I would obviously wish that our most senior politicians were able to hold two environmental thoughts at the same time - but there is a political reality; climate change is sexy, so we get most traction there."
which means this is where groups such as the RSPB are likely to focus most of their lobbying.
Former UK Environment Secretary John Gummer is clear that concern about climate impacts on the natural world is not the only reason why conservation groups are increasingly taking up the climate banner.
"I think we've got to be very blunt about it; campaigning groups for the environment or anything else are in the marketplace.
"So if you want to raise money to do something about the marine world (for example), you do it by campaigning on dolphins.
"It's exactly like a business, and in that sense we have to realise that the choice they make is with mixed motives. This is not a criticism, but they are as likely to be partial in what they choose as any business or any politician."
To a large extent, environment groups set the concerns of the environmentally aware citizen; so if they prioritise climate change, perhaps that means a loss of awareness of all the other things that people might be - or used to be - concerned about.
On the global stage, loss of biodiversity - in plain speech, loss of nature - is one of the issues you will rarely hear leading politicians lamenting - despite the fact that governments pledged to do something about it as far back as the Rio Earth Summit of 1992, at exactly the same time that they were pledging to do something about climate change.
Deutsche Bank economist Pavan Sukhdev leads a UN-sponsored project aiming to quantify the economic costs of losing the "goods and service" that nature provides - something, he says, on which the evidence has been ignored for far too long.
"Work in this field has been going on for so long that it is a shame the idea of pulling this together and presenting it to the public and to governments as an issue wasn't done earlier."
Preliminary calculations indicate the cost of forest loss alone dwarfs the cost of the current banking crisis - a conclusion that has been met with resounding silence at the political level.
A much more comprehensive analysis is due for publication next year; but he is not holding out too much hope that it will sway minds.
"Climate change is already occupying mind space and heart space, and for biodiversity to occupy the same space is going to be a challenge."
Even more difficult than putting something like biodiversity loss on the agenda, says former government adviser Jonathon Porritt, is getting politicians and the wider environmental community to accept that underpinning everything are the unsustainable size of the Earth's human population and our unsustainable (and rising) hunger for the Earth's natural resources.
Recently he raised the population issue in his blog - only to be excoriated by columnist Melanie Phillips for having a "sinister and de-humanised mindset" - which is perhaps an indicator of why other contemporary environmental thinkers are so reluctant to raise it publically, despite admitting its importance in private.
Traffic pollution still causes thousands of deaths per year in rich countries
"Too controversial," he says.
"Population raises all these issues about religion, about culture, about male dominance in the world; and (people) get very uncomfortable about that."
Nevertheless, he argues, the logic is undeniable.
Speaking recently at Mr Porritt's Forum for the Future, a Chinese government official described the one child per family policy as having led to "400 million births averted" - which she then converted into the greenhouse gases those extra human inhabitants would have produced, and noted that no other country had done as much to curb climate change.
But, he continues: "You don't have to accept the China route to that logic.
"You can look to all kinds of alternative ways of reducing human numbers which aren't done as coercively as the one child per family policy was done in the past.
"However, when I was director of Friends of the Earth, could I get our local groups or my colleagues to go along with that? I have to admit complete failure."
In contrast to the 1970s, the decade of the first global attempts to look at environmental decline, population is not now on the political radar.
Neither is the question of whether stopping that decline is possible without deep reform of the world's economic system.
Biodiversity loss, desertification, unsustainable fishing
where are the spaces at the top table for these?
By singing the climate tune so loudly, have environmental groups unwittingly helped to create a situation where climate change is all that politicians and the public hear?
Has the media contributed? A couple of years ago I added up the number of articles we had written on the BBC News website within the preceding nine months about various issues.
The scores were four for deforestation, four for desertification, 17 for biodiversity - and on climate change I stopped counting when I reached 1,000.
In large part, what journalists report reflects what is going on in the big world; but have we, too, forgotten the larger messages of the UN Geo-4 report, the Millennium Ecosystem Assessment, and other audits of a society whose environmental problems run much wider and deeper than climate change?
None of the people I interviewed for the programme argue that man-made climate change is not real or not important; there is no suggestion of a swindle here.
Some believe a narrow focus on climate is justified - either because they feel it is so much more serious than every other issue, or because they feel there is real political momentum to solve it now and time enough to deal with everything else once that is done.
But others argue there is no time; that society needs, urgently, to see the wider picture of global decline in all its complexity - and that climate concerns have hijacked the broader agenda, to the detriment of us all.
The Great Climate Change Hijack is broadcast on BBC Radio Four at 2100 BST in the UK on Thursday 27 August