This book is written for ecologists interested in capturing their understandings of how natural systems work in software – to help inform their work and communicate the consequences of proposed management plans.  Historically, ecologists had to rely on the skills of trained computer programmers to modeling natural systems, but now a new generation of software is allowing ecologists to directly capture their understandings of systems in software.  This book is a compilation of spatially explicit simulation models developed by ecologists and planners without any formal computer programming skills.  Readers will be inspired to believe that they too can create similar models of the systems with which they are familiar.