How can researchers understand if a human activity, such as pollution, negatively affects the abundance of a native species in a short amount of time? Measure the density of the native species in a single location for many years. If pollution negatively affects the native species, there will be a negative correlation between the density of the native species and pollution. Measure the density of the native species in many different locations. Measure the density of the native species and a range of intensity of pollution in many different places. If pollution negatively affects the native species, there will be a negative correlation between the density of the native species and pollution. Measure the abundance of the native species in different places that might have been affected by different pollutants.