Lakes come in many shapes and sizes, from small urban ponds, through constructed reservoirs, to the largest transboundary lakes. Collectively, these ecosystems are critical in supporting many societal needs. These include the provision of food and clean water, navigation, achieving Net Zero Carbon climate ambitions and renewable energy production, reversing biodiversity loss, delivering national and international food and non-food trade objectives, supporting livelihoods and creating jobs.
The current environmental status of lakes is one of large-scale degradation, threatening their societal and economic value and incurring significant loss and damage. One of the main pressures globally is nutrient pollution from agriculture and wastewater, although effects of climate change, plastic pollution, hydrological alteration, industrial waste discharges, invasive species infestations, and habitat destruction are also prevalent.
'Undervalued, understudied, and overlooked'
The current global approach to lake management is inadequate. Local to global management responses remain fragmented, under-resourced and undervalued. If left unchecked, societal impacts are predicted to substantially worsen in the coming decades. Global analyses project that by 2050 these impacts will include a decrease in the value of ecosystem services (currently estimated at $US3 trillion) by up to 20 per cent; a doubling (at least) of nutrient pollution from agriculture and wastewater, costing hundreds of billions of dollars a year to address; increased methane emissions from lakes with global societal costs estimated in the trillions of dollars; and a further increase in the rate of biodiversity loss from freshwater ecosystems, which is already higher than in any other biome.
Lakes and reservoir ecosystems are undervalued, understudied, and often overlooked. Yet, they are of crucial importance for food security, the provision of clean water for drinking and irrigation, energy production, navigation, recreation and biodiversity. The global value of freshwater ecosystem services is in the order of trillions of dollars. 1 The importance of exposure to nature in managing mental health and improving well-being is also becoming increasingly apparent. For example, access to 'blue-green spaces', including lakes, reduced mental health impacts of severe lockdown during the COVID-19 pandemic. 2
117 million lakes
Using satellite imagery, it is now possible to map and monitor the extent of lakes on earth. The Global Water Body Database, provides information on about 117 million lakes (> 0.002 km2 surface area), covering 5 x 106 km2 of the earth's surface, 3.7 per cent of the non-glaciated surface area. 3 About half of all lakes (one quarter the global lake surface area) are located above 60oN and large lakes account for only 0.05 per cent of lake number but over half the global lake surface area. 4
Growing concern
It is of growing concern that lake degradation continues to be reported globally. One-fifth of the world's river basins (including lakes, reservoirs and rivers) are experiencing above-normal changes in available surface water. 5 The loss of species and their habitats is recognized as an international crisis, particularly in freshwater where threats of species extinctions are greater than any other major ecosystem type (estimated as an average 84% decline in species over the last half century). 6 The causes of this biodiversity loss are many, including habitat destruction or alteration (e.g. hydroelectric dam construction), mining, invasive species spread, and nutrient pollution. Rarely do these pressures act in isolation, and climate change likely exacerbates their effects, and complicates their management.
- Adapted from Embedding Lakes into the Global Sustainability Agenda 7
1 Costanza et al, (2014).
2 Pouso et al, (2021).
3 Verpoorter et al, (2014).
4 Pi et al, (2022).
5 UNEP, (2021c).
6 WWF, (2022).
7 WWQA Ecosystems, (2023).