GIVEN my role as a Green MSP, it's not unusual that I'm invited to speak about the environment to a group of modern studies students.

But the most recent example was bound to be a little different - as this group of students were inmates in Barlinnie.

It was only my second visit to the prison, the first having been to support a young, openly gay French anarchist who'd been arrested at a protest against the G8 meeting in Gleneagles.

Nobody would have wanted to be in his situation, but standing out so much from the crowd made him particularly vulnerable.

Separated from his friends who weren't being allowed in to visit him, he had no idea how long he would be held and was feeling understandably insecure.

I suppose my job was mostly to reassure him, but I have to admit that even as a visitor the place made me feel pretty anxious, and I had to work hard to hide that.

This week I arrived out of breath and having broken a sweat - Cumbernauld Road is quite a hill to climb on a bike - and after the complicated business of getting through security I met some of the staff in the education centre.

The place is pretty intimidating (maybe unavoidably, maybe intentionally) and I can only wonder at their ability to engage with the inmates in that environment.

I had been advised to try not to make my talk sound like a lecture, so I tried to keep it informal. Alongside a speaker from RSPB and another from Friends of the Earth we talked about climate change, Scotland's wildlife, renewable energy, and a host of other subjects.

Some of the students wanted to ask questions about the environmental issues we were there to talk about, while others wanted to talk about their own situations, rehabilitation, drug laws, and more. Others of course were less engaged, and perhaps just saw it as a chance to be out of their cell block for a couple of hours.

There was one idea I was keen to get across, and I don't know how successful I was.

A core idea to Green politics is that environmental destruction and social harm are often linked to the pursuit of everlasting economic growth, which is both impossible to achieve and distracts us from the things which really matter in life.

Constantly trying to generate more economic activity can undermine our health, our relationships with one another, and our communities.

But it also ignores the difference between positive and negative economic activity.

For example a lot of crime generates economic activity, making work for lawyers, doctors, insurance companies and the like; so does building prisons.

But nobody would imagine that more crime and more prisons is a sign of a good society.

I've no idea whether I got the idea across, or what they really made of it.

But I've often found that it's an argument people can understand in their own lives, even if most economists and politicians can't accept it.

Of course after my talk I left, and they stayed.

I have to admire the people who are trying to give them something meaningful to think about, to make their time inside useful to their chances of a better life when they leave.