Methods

We modeled the current distribution of urchin species using a point process approach, which is well suited for presence-only data. Spatial point processes are models used to describe point patterns that are spatially distributed. This can be, for example, the occurrence of landslides or the records of a species. Those models have been shown as a solution for modeling presence-only data, avoiding the necessity of sampling pseudo-absences, and presenting several advantages for modeling species distribution. Point process models (hereafter, PPM) can be described through a Poisson process, where the point pattern is fitted by an intensity function. SDMs are usually modeled through a non-homogeneous Poisson point process, where point events are independent of each other and where the intensity varies spatially (i.e. there is a spatial trend).