In the 1960s, acid rain severely impacted freshwater ecosystems in Ontario, causing significant declines in fish and microscopic species. A study published in the journal Proceedings of the Royal Society B examined how the copepod species Leptodiaptomus minutus adapted to these changes. Researchers utilized 'resurrection ecology' to analyze sediment cores from George Lake and Lumsden Lake, revealing that copepods evolved traits favoring survival in acidic conditions. These adaptations included faster development and maturation rates compared to pre-acidification populations. Remarkably, after environmental improvements in the 1970s, copepods exhibited increased sensitivity to acidity, suggesting an 'adaptive reversal' of traits. This study provides a rare real-world example of 'evolutionary rescue', highlighting the complexities of species adaptation to environmental changes. However, the historical acidification also raised concerns about reduced genetic diversity and population sizes, which could hinder future adaptability to ongoing environmental changes. The findings emphasize that ecological recovery does not restore previous conditions, as species continue to evolve in response to changing environments.