Long-term trends in productivity across Intermountain West lakes provide
no evidence of widespread eutrophication
Abstract
Eutrophication represents a major threat to freshwater systems and
climate change is expected to drive further increases in freshwater
primary productivity. However, long-term in-situ data is available for
very few lakes and makes identifying trends and drivers of
eutrophication challenging. Using remote sensing data, we conducted a
retrospective analysis of long-term trends in trophic status across the
Intermountain West, a region with understudied water quality trends and
limited long-term datasets. We found that most lakes (55%) were not
exhibiting shifts in trophic status from 1984-2019. Our results also
show that increases in eutrophication were rare (3% of lakes) during
this period, and that lakes exhibiting negative trends in trophic status
were more common (17% of lakes). Lakes that were not trending occupied
a wide range of lake and landscape characteristics, whereas lakes that
were becoming less eutrophic tended to be in more heavily developed
catchments. Our results highlight that while there are well-established
narratives that climate change can lead to more eutrophication of lakes,
this is not broadly observed in our dataset, with more lakes becoming
more oligotrophic than lakes becoming eutrophic.