Be sure your map is mapped to a large enough area of your scene for your Ecosystem objects to fit in, at the object density you want.

A common problem is for vegetation to overlap some of your mapped areas because you made those areas too small to hold the vegetation.

I did this myself on my first couple of Ecosystems, lol.

HTH

_ jc...'Art Head Start' e-book
.......'Art Head Start.com site Digital Art skills. Free lighting chapter, tutes, Vue models, tex pix.