To determine if a plant is expanding or contracting its range the straightforward task of a survey to map the spatial extent of a plant population is an effective monitoring method.
This method is also known as boundary mapping and when done every year or two can provide valuable insights into the fate of a species population. To map a plant population the surveyor must be able to identify the species accurately including both fertile material and vegetative characters so that the survey can be completed even when it is not in flower or fruit. The surveyor must also be able to locate sites on a map and be able to accurately describe the spatial extent of the population on a map. If a GPS is used then the operator must be skilled in the use of this equipment for mapping. Low-level aerial photography may also be useful for mapping the extent of a species population.