A group of Dutch scientists has been trying to predict when lakes will enter ecological crises by monitoring key tipping points.
Researcher Alena Gsell, of the Netherlands Institute of Technology, says the term ‘tipping point’ has become popular to describe sudden and fundamental changes that take place even though exterior conditions haven’t changed as radically.
Once such a shift has occurred, it’s difficult or even impossible to get things back to the way they were. But that doesn’t mean there are no alarm signals. There is in fact a whole range of statistical indicators that have been proposed as possible early warnings.
“We’ve looked at five lakes for which long-term monitoring data is available,” said Gsell.
The good news is that in some cases, early-warning indicators were indeed detected up to several years ahead of the moment when a ‘regime shift’ would take place.
“That leaves some time for water managers to step in and take appropriate measures,” Gsell said.
These indicators show that the resilience of lake ecosystems becomes less ahead of a regime shift.
“It’s something you can observe if you know an ecosystem well”, said Gsell.
Perturbations become bigger. Water turns turbid temporarily, smaller zooplankton species are favoured and edible green algae lose ground to the less tasty blue-green algae.
For the early alarm signals to be more effective, argue the researchers, collecting long-term data — an essential ‘window into the past’ — isn’t the only thing that’s important. The methods for mining the data also need to become more advanced and data needs to be collected more frequently.