When I looked at the website (looking impressive btw) I didn't notice an itinery anywhere- is this because it's top secret? Or they haven't decided yet?
If they are going for 4000 species, a lot of the travelling is going to have to be between neighbouring countries, which will minimise the long haul flight component. A year's travelling is going to use up a lot of CO2 admittedly, but probably less than doing all those countries as separate trips. As long as when they do come back they live out the rest of their days in a straw bale house, plant trees all day long and bury their poo deep underground it might all equal out . . .
I read on their diary that they expect to be passing through Gatwick/Stanstead several times, with trips to Ecuador, Finland, Brazil and Spain, among other destinations. Now considering a return flight from London to New York releases about 1.5 tonnes of carbon, while the average carbon footprint for a British resident is around 11 tonnes (perhaps about double what's globally sustainable), you have to imagine all the flights this couple are going to undertake, plus the hotels, taxis and car travel, it's going to add up to something quite sizeable.
On top of that, their diary tells of previous birding trips around the world, so big though their plans are for 2008, jetting around the world is hardly new to them.
Of course it's very easy to be holier than thou about all this, but on the other hand, when well-meaning 'conservationists' have a bad idea, it really ought to be pointed out to them.
To put is another way, raising funds and awareness for conservation project in Ecuador is one thing, but do you suppose the indigenous peoples of the Arctic are exactly going to be applauding rich people jetting all around the world on 'eco-holidays' while their homes are melting from underneath them, particularly as we're all well aware now that needless air travel has an expanding influence on the plight of the Arctic? Who knows, maybe they will.
Ultimately, this is an example the typical Western conservationists disease, that notion we can do whatever we wish, choose luxuriant lifestyles that we know aren't sustainable and which do damage to the planet, we can do it all with impunity, so long as we mean well and have membership of the National Trust or RSPB or whoever else. A disease, I might add, which frankly, I'm something of a sufferer of myself.