Deforestation: many of what are our picturesque moorlands in the north are due to humans deforesting them, and deliberately keeping any trees from growing on them. They did this initially to bring up sheep on the cleared areas, then the habit spread, and after the Victorians became enamoured of these 'wide, wild' places, they've been kept bald ever since.
Dams - completely unnatural, change the course of rivers and affect silting, tidal currents, habitats, etc., but DO light up lovely, natural places like Las Vegas. :blink:
Golf courses: appallingly barren to wildlife, moles especially; take up far too much water resources to maintain and are 'enjoyed' only by a paying few in ratio to their vast areas. Now spreading in their thousands, worldwide, in a golf pandemic.
Racecourses: see above.
Airports: encourage cheap air travel, millions more flights, and the befouling of the skies with vaporised fuel. Major contributor to global warming. Not to mention miles of concrete, utter anathema to nature.
Car parks, industrial size: concrete, concrete, concrete. Hot, barren, entirely hostile to nature.
Herbicides, pesticides, all 'cides': aim is to kill any living creature in gardens, on crops, roadside verges, trees, etc. Along with the beneficial creatures which nature evolved to cope with the pests. Millions of miles of 'nature' affected daily.
Colin, I don't think your wife's doing much to upset the so-called balance of nature! It's pretty much been wrecked by humans, so any redress, however tiny, is welcome.