  In a series of notes we explore the detector requirements of the forward
tracking region for a future $ e^+ e^- $ collider with a center-of-mass energy
in the range from 500 GeV to 3 TeV. In this first part we investigate the
relevance of the forward region for a range of physics processes that are
likely to be relevant in such a machine. We find that many examples can be
found where excellent performance of the forward detector system may lead to a
considerable increase of the physics output of the experiment. A particularly
clear physics case can be made for the reconstruction of electrons at small
polar angle.
