What is 'church'?

Deborah and I have been chopping wood again today in the Provencal sunshine. All that physical work and blisters let my mind wander. It got me thinking whether 'A Rocha' is a church.

As an organisation their vision is for each project to stand for the following values:

CHRISTIAN charity; committment to CONSERVATION; CAMPAIGNING for the care of God's world; drawing on CROSS-CULTURAL strength of the world-wide church; each project having a distinctive COMMUNITY emphasis.

In practice they live in outward looking communities, they have a definite mission focus on science, research, practical conservation and environmental education and people join the community and become christians. They also pray, study the bible and worship God, so are they a church?

Ok, they don't baptise or take communion (not that I've seen) but neither do the Salvation Army.

Could 'A Rocha' type communites be an answer for the declining church in the West, prophetic communities with a specific mission focus, whether it be conservation, skater kids, or simply young families with kids?