Liming, adding of limestone or dolomite, has been conducted for many years in order
to mitigate the acidification of lakes caused by ‘acid rain’. However, despite the longterm
application of liming in many countries, there is still debate on the impact of
liming on lake biota. Hence, we conducted a systematic review and meta-analysis in
order to answer the question: What is the impact of ‘liming’ lakes on the abundance
and diversity of lake biota?
A systematic search was conducted for all relevant papers using search terms for
liming combined with terms for lakes and the biota. All articles found were included
if they report on a study containing a relevant population (the biota in freshwater
lakes), intervention (liming), and outcome (change in abundance/density or
richness/diversity of biota).
The search found 143 relevant articles. The available evidence suggests that on
average liming increases the diversity of fish, zooplankton and phytoplankton,
whereas the diversity of benthic organisms is not increased. The diversity of
zooplankton and phytoplankton is estimated to decrease in some lakes but only in a
small minority. The meta-analysis on the abundance of zooplankton, phytoplankton,
and benthic invertebrates indicates they do not increase with liming. The impact of
liming on fish abundance is less clear cut. The largest fish study suggests fish may
increase in abundance with liming. However, there is a lack of studies with both
baseline and control sites, making it hard to be certain whether the changes observed
were due to liming. Liming has also been used to restore fish abundances by
providing conditions for survival of stocked fish. The liming appears to have enabled
the restocking of fish in some instances. However, many studies did not actually test
if fish would have survived before liming or stock fish in control sites.
Increasing and preserving the diversity of organisms present in an ecosystem can (but
may not always) represent a favourable ecological outcome, especially if achieved
across a broad spectrum of the ecosystem and of acid sensitive species that were
previously absent due to acidification. In this regard liming of lakes can be
considered, in some circumstances, an effective conservation measure. However, in a
minority of lakes diversity decreased with liming. The evidence base is insufficient to
explore reasons for variation in effectiveness and more powerful study designs are
required to enable prediction of when extremes of impact may occur.
Liming, lakes, biota, zooplankton, phytoplankton, benthic organisms, macrophytes, fish.
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