Convert all church parking lots into community gardens (and later all churches into community gardens + food education centres + seed vault)
No matter where you live, there are always a handful of churches within walking/biking distance. Why not think green, walk / bike to church and convert the unused parking lots into community gardens so that non-church-goers benefit as well? That would be a good first step.
And wouldn't it be more intimate if church groups gathered at each others' homes taking turns to host rather than going to a mega church where you don't have time to greet everyone? So hopefully in the future we will see more church goers gather in smaller groups instead and then churches can be converted to community gardens / hydroponic vertical farms / honey bee farms / seed vaults / food learning centres (for kids) benefiting everyone in the community, regardless of age/race/gender/faith/income. That would be a great next step.
If christians / churches can take the lead and do this for their communities, then we may see temples / monastery / mosques doing the same as well.