  We look at buildings' competition over space in cities through the lens of
ecology.
  Adopting the convex hull of the building's footprint perimeter as a
definition of species yields parallels to forest trees' competition, which we
expound on. Their perimeter distribution $p(r)$ follows a power-law behavior
beyond a critical threshold of the density of the built environment. In this
regime, the species coexistence likelihood $p(d)$, where $d$ is the distance to
the nearest competitor, which we define to be a building with a larger $r$,
bifurcates with the buildings' number $n$. This reveals two different predation
laws: a vicious predatory one which is linked spatial homogeneity and
segregation, as opposed to another favoring spatial diversity and intermixing
between species.
