Like humans, lakes can suffer from a wide range of health problems: from high temperatures to circulatory, respiratory, nutritional or metabolic problems to infections and poisoning. Researchers led by the Swedish University of Uppsala and with the participation of IGB, have highlighted this in a recent study. In order to protect lakes from chronic diseases and threatening conditions and to heal them, strategies similar to those used in human healthcare should be applied: Prophylaxis, regular screening, treatment and mitigation on a local to global scale.
There are 1.4 million lakes worldwide with a surface area of more than 10 hectares. Around 12 per cent of the world's population live within 3 kilometres of these lakes and use them for drinking water, fishing, recreation and tourism. However, lakes can only fulfil these important ecosystem functions if they are in a good health state.
In a recent study, researchers suggest using human health terminology and approaches to assess and treat the world`s lake system issues. For example, lakes with multiple health problems could be labelled as ‘multimorbid’, and regular screenings similar to human checkups, could help to detect issues in lakes early on. ‘The analogies illustrate that lakes are living systems that need oxygen, clean water and a balanced supply of energy and nutrients,’ said Dr Gesa Weyhenmeyer, a scientist at Uppsala University and first author of the study.
The team used LakeATLAS data from the global compendium HydroATLAS from around 1.4 million lakes worldwide to examine lake maladies of the circulatory (such as floodinig and drying out), metabolic (such as acidification and salinisation), nutritional (such as nutrient excess) and respiratory (such as oxygen deficiency) disorders, along with other types of disturbances.
Assessing the state of health using reference conditions
But when is a lake healthy – or sick? Many countries have made substantial progress in assessing the health status of their freshwaters in recent decades. There are approaches, such as the European Water Framework Directive, to harmonise these assessments across countries.
A key concept of lake health assessments is the comparison of the present status with reference conditions, often defined as conditions that prevail in the absence or near absence of human disturbance. ‘The approach to assessing deviations from reference conditions is similar to practice in the health sector. However, so far there is no simple global system to classify the health status of lakes,’ said Dr Sabine Hilt, scientist at IGB and co-author of the study.
Typical diseases affecting lakes around the world today
1 Severe circulatory problems: 115000 lakes lose twice as much water by evaporation as they receive
Circulation in lakes refers to the availability and dynamics of water. One serious circulation problem with numerous cascading effects on the health of lakes is desiccation. Researchers estimate that around 115000 lakes worldwide evaporate twice as much water as they receive from direct precipitation. This makes them particularly susceptible to drying out if the tributaries also dry out. This jeopardises more than 153 million people who live near these lakes.
