Answer: Measure the density of the native species in many different locations.
Step-by-step explanation:
Native species is the one which is inhabitant of an area or location for a prolonged period of time. To determine the impact of population on the native species researchers must check upon the overall density of the population of species at distinct locations as many native species can migrate to different locations in search of food, water, shelter, and mates. At the site being migrated the native species may experience less pollution as compared to native site and if their mortality rate is less than the native place then this means that the native site is not suitable for the survival of the species because of pollution.