You may have seen the leaflets about the campaign against the development of the County Ground (their website is at www.howzatgccc.org.uk).
One aspect of particular relevance to St Andrews Park is the proposal to build accommodation for 350 students, for whom the park will be their nearest green space. Personally I'm not sure that the addition of another 350 students (and their friends) on a nice summer's day will benefit the amenity of the park for the other users.
There are many other reasons for objecting to the proposals too (limitless Elton John sized concerts, massive traffic disruption, no additional parking for students or spectators etc. etc.).
Details of how to object can be found on the howzat website.