[teragram (OP)]

It is proposed that in the near future most houses will be built using ground source heating instead of gas heating. I am fully in favour of such schemes, but given that, according to one estimate, an average house requires 300 - 700 square metres of  land to accommodate the heat collecting pipes, in areas of high density housing (surely the largest sector) how can sufficient heat collecting pipes be accommodated. Given that an enormous quantity of heat would be extracted from the soil, what effect would the lowering of temperature have on the flora and forna in and on the soil? If the solution to these problems was to be the use of air source heat pumps,  would the effect on the outside temperature lead to similar problems, ie more severe frost when wind speed is low.

[alancalverd]

Ground source heating is fraught with problems, not only of infrastructure but also of diminishing efficiency in times of high demand as the ground freezes around the pipes. Airsource heating is a lot easier to install and maintain: I use a single fan unit of less than one meter square to heat and provide hot water for a family in a 1600 sq ft (160 sq m) building. It works with air temperatures down to about -5 degC and a reversible unit would also provide summer cooling (very important in high density cities). No problem with increasing source impedance - you just blow more air through on a cold day. Wind speed is irrelevant as the fan is rated for zero wind, and any air movement just helps a bit.

The real key however is efficient building design. Mine is massively insulated with a huge hot water tank. I have architect friends with a completely passive house in Maine, where even in mid winter a south-facing glass wall provides all the heat they need to keep their huge concrete slab floor warm. A builder friend in England has made three terraced town houses with passive, heat-exchange and air-source heating that demonstrate how to achieve high density and thermal efficiency. 

[teragram (OP)]

Ground source heating is fraught with problems,... 

Thanks for your comments. My concern with large numbers of air source heat pumps and wind is more to do with the ambient outside temperature. I would think that on occasions when wind speed is very low or zero, large numbers of heat pumps may cause pooling of frigid air in the locality. A breeze would replenish the supply of air, and move pooled cold air away. My garden is on a gentle downward slope towards the house, with high fences on each side. I would think that an air source pump would cause a quite deep layer of very cold air to accumulate against the wall of the house.
I agree entirely that insulation is key to solving many of the problems of heating buildings, but in many cases there are problems with installation.

[Bored chemist]

I would think that an air source pump would cause a quite deep layer of very cold air to accumulate against the wall of the house.

Occasionally, entropy is on your side.