Obviously the building of houses changes this, and in some people's minds adversely as the 'natural' feel is lost and replaced with a human dominated landscape. Many people however wish to live on the Hills for the views and to be above the smog layer. As the economic fortunes of sheep and cattle farming have declined, so to has the viability of pastoral farming on the Port Hills. For some farmers it is simply uneconomic and they have sought ways to get a better income from their land. One of these is the introduction of exotic forest.
Trees grow well on the hills, especially the upper slopes where the rainfall is higher.
But again the trees have the potential to change the existing character of the Hills, from one of an open tussocky landscape to that cloaked in dark green forest. As discussed above, the Port Hills have undergone some rapid and marked changes over the last 400 years, from being covered primarily in native forest to that which is there today. All this change has meant much stress for the remnants of the indigenous plant and animal life. Present threats include possums, rabbits stoats, and weeds such as the South African boneseed bush. Parts of the Port Hills are susceptible to erosion, which endangers lives, reduces pasture areas, causes unsightly scars and contributes to problems with stormwater drainage.