And there it was. Boom. Back in London. Having cycled 3,000km, through eight different countries, to travel from the source to the mouth of the River Danube in just three weeks. That question was a sharp and sudden reminder that we were now back home, back on the bike, and back commuting to work. The adventure was over.

And what a surreal moment. There I was, waiting for the traffic lights to turn from red, surrounded by other bicycle commuters and listening to a stranger next to me trying to persuade us all that we hated cyclists. He was incensed by all the bikes careering straight through the red light and flying into the line of merging traffic filtering through its own green light from the right. ‘There’s just too many of us now!’ he exclaimed, ‘We’re a danger to ourselves, let alone others!’

He was referring, of course, to London cyclists and he is certainly right that the number of bikes on the City’s roads has exploded over the last few years, to the point where the first hazard that bikers have to take on is the crowd of other cyclists already on the road.

‘Why doesn’t everyone play by the rules and stop at the reds? There’ll be a pile up sooner or later and any one of us could get hurt.’

His question set my mind racing; individuals playing by the rules for the good of everybody, eh? You see, our ambition to cycle the length of the Danube this summer wasn’t simply the product of three guys getting a bit carried away over a few jars one evening (though that did play a significant role). With 2010 being the International Year of Biodiversity, and the three of us sharing a deep interest in sustainability issues, we had decided to explore the range of unique habitats connected by ‘Europe’s answer to the Amazon’ to find out what local people from across the continent think about the value of biodiversity.

It was a truly fascinating journey. The challenges and delights of bicycle touring through eight different countries were justification enough for the trip; from strangers in Serbia welcoming us into their houses to try and help us fix broken wheels to Romanian children dashing out from the shade of the trees to give us a ‘high five’, our experience of new European cultures was both humbling and inspiring.

But just as importantly, with the help of international charities like WWF, we stopped off at a number of National Parks and nature reserves on the way to meet people known to have really strong views about their local biodiversity. The passion and dedication of people like Georg Frank in Austria and Jasmin Sadikovic in Croatia was overwhelming and we learned a great deal about the value of biodiversity in these local contexts.

From burgeoning eco-tourism projects in rare wetland areas to farmers being paid by governments to protect birdlife, we came across all sorts of people benefiting directly from working in partnership with the natural world around them. Perhaps the most memorable example was the Bulgarian vineyard relying on ladybirds to keep pest populations down without incurring the costs or side-effects of chemical pesticides!

But when we finally arrived at the Danube delta in the Black Sea, elated but exhausted, we had some time to reflect on everything we had seen on the way. Something was troubling us.

It may have just been the way we organised the trip, but virtually all of the biodiversity projects we visited were in National Parks or the equivalent – spaces where natural and human activities are kept as separate as possible. Furthermore, the great work we had learned about was so often led by passionate voluntary sector organisations, who all shared a common experience – their struggle against ‘the system’.

This didn’t feel right. Even the world’s leading economists are now arguing that the rate of biodiversity loss is costing humanity dearly and it is an absolute no-brainer to get on and do something about it, on a global scale. So why is real action still limited to the local, passionate few?

The traffic light incident, back on London’s streets, put an interesting perspective on things. The chap next to me, asking ‘Who hates cyclists?’ was making a simple enough point. Despite the fact that any one individual can probably jump a red light and survive, if everybody starts ignoring the traffic lights, chaos quickly ensues as one of the fundamental systems in place to help our roads function in as safe a manner as possible becomes null and void. Then everyone starts losing out and people get hurt.

So the question is: What is it that will persuade the individual cyclist that it is actually in everybody’s interests, including theirs, to respect the underlying traffic systems on which we are all reliant? Will it be a near-miss with a car? A friend having an accident? Police at every junction? An open question...

But the parallel with our thoughts at the end of Biking for Biodiversity is interesting. As a species, we know how important biodiversity is to human life. We may not think about it every day, but science already understands that if you artificially reduce the natural range of living species in any one area, and the complex relationships between those species in the process, you compromise the stability and resilience of the ecosystem itself, something critical to supporting human life.

We also know that humans derive all sorts of currently unvalued benefits from the natural world, from pollination to climate regulation, and that the variety and spice of living things is crucial to the healthy function of those services.

But somehow, beyond the converted few – such as those we met on our cycle along the Danube – we as a human species find our reliance on biodiversity too difficult, too intangible, too complex a dependence to behave in a way that recognises that a little bit of change to each of our behaviour actually benefits the whole, including us, the individual.

So we continue to decimate ecosystems, to kill off biodiversity, with or without malicious intent, and stretch nature’s resilience to breaking point. There is some fantastic work being done now to engage one of the most powerful levers for change we know of – the market – on this subject, but Biking for Biodiversity implied to us that we need hearts to change with minds, too, to achieve the full change that is necessary.

How many giant oil spills will it take to make us realise, as a species, that the natural world – on which we depend – has its own traffic light system?

And that the signal is on red.