By Alex Kirby BBC News Online environment correspondent

Day six of Alex Kirby's diary from the World Summit on Sustainable Development in Johannesburg.

Every now and then reality just refuses to be kept at bay. Today was one of those days.

I've spent most of the last week cooped up in the richest square mile in Africa, mixing with well-intentioned people (most of them) doing their best to make the poor less poor.

Some [Aids sufferers] ... live out their remaining days on abandoned mine dumps, away from human contact

It's anyone's guess whether they'll be able to make much difference.

Today, though, I went to the world's biggest hospital, on the edge of Soweto, to see an environmental improvement scheme.

On the way back to central Jozi, the people who'd taken me to Soweto suggested we stop briefly at a hospice for HIV-Aids sufferers.

I didn't know what to expect - horror, squalor, resignation, despair.

I didn't find any of those. What I did find was life.

Saving the 'sparrows'

The Sparrow Ministries project, as its name suggests, is a Christian enterprise.

For years it struggled. Now it has a proper settlement of simple round brick huts.

The hospices try to provide sufferers with a little dignity

It provides in-patient care to 35 adults and 48 children and other community-based services as well.

It has grand plans for expansion.

We went to the children's part of the Rainbow Village.

Children swarmed like bees as we entered, entwining themselves about us, wanting to be picked up, played with or just held.

We saw one six-year-old playing happily with a hoop.

He was the size of a British child of two.

In this part of Gauteng province, 42% of the miners are known to be HIV-positive.

Brief lives

How many other adults are affected nobody knows.

Some of those who have succumbed go to live out their remaining days on abandoned mine dumps, away from human contact.

Some of the children are brought... by the police, who find them when they collect their parents' bodies from the city streets

Others are found by animal welfare workers as they search for injured or neglected animals on rubbish dumps and in scrapyards.

Some of the children are brought to Sparrow's Nest by the police, who find them when they collect their parents' bodies from the city streets.

It's rare for any of them to survive much beyond the age of 10.

Most of them were bubbling with laughter but I was struck by one little boy who refused to respond at all apart from placing his cold hand in mine.

When we left, though, he waved goodbye.

Good intentions

We watched a brief video about the work of the hospice.

One woman shown in it was gaunt and looked worn out.

She died this morning.

It would be cheap to say that those who end their days in Sparrow's Nest are there because of the policies of the captains and the kings assembled at the summit a few miles away.

I hope, for all that, the summit can make places like the hospice unnecessary.

I've spent most of the week doubting the delegates' ability to achieve very much.

Today, I really would love to be proved wrong.