The study looked at how barnacle populations change in size across different areas they live in. They found that populations at the edges of their range have more fluctuations in size compared to those in the middle. This is because environmental changes affect the populations more at the edges. The researchers also discovered that as the population size increases, the variability in size decreases. This means that the bigger the population, the more stable it is. Overall, understanding how population size changes across different areas can help predict how populations will fluctuate over time.