LQQK,

Another problem that occurs with trees is *reduction* of the
groundwater from evapotranspiration in clay soils, consequent
consolidation of the clay stratum, and settlements of the structure
founded on the stratum. This is usually associated with large trees
like oaks so a relatively small pear tree may not apply... The thing
is, you neighbour by watering may be balancing the equation.

Is this caused by the roots taking moisture out of the soil?

http://www.marinwater.org/evapotranspiration.html

Taking this on a tangent, we can literally go 7 months without any
rain and plenty of dry baking heat, and so this highly expansive clay
really dries out around our foundation, one idea I've heard is to put
in irrigation drippers around the foundation to keep the moisture
content consistent year-round. Do you have any opinions on doing
that?