Eco-House Went Bad

This was building made very eco friendly and was said to show people the beautiful forests of Mexico. But the article says,the owners of this plot of land had an exceptionally difficult series of problems to work around: the land was .5 hectares (about 1.2 acres), covered in slopes and pitted with collapsed caves left over from previous mining on the property. The very small flat, treeless portion of the land had to be used for parking. But maybe most challenging of all was that the existing plant life had to be left untouched. In the end, about 97% of the land was unsuitable for building on. 97% is a huge number to have if it is bad for the land, i really want to know why they would build on the land if it was not good enough.