A new study published in Nature Communications shows that over the last 40 years, the surface area of lakes worldwide has increased by more than 17,760 square miles, which is larger than the entire nation of Denmark. This influx of new lakes raises concerns about global greenhouse gas (GHG) emissions and highlights how vital it is that we understand the quantity, size, and development of these lakes to address the issue properly.
Researchers from the University of Copenhagen, the University of Hong Kong, and others have created a “more accurate and detailed” map of the world’s lakes to date. The map includes 3.4 million lakes along with how they have changed between 1984 and 2019. Over half of this expansion was due to the construction of reservoirs.
The research team’s calculations indicate that previous estimations may have been overblown; a 2016 study posited that global lake CO2 emission was 571 teragrams of carbon annually, but this new study calculated only 226 teragrams emitted annually. However, the team adds that the estimations are “conservative.” As such, efforts should still be made to curb GHG emissions.
The team also found that small lakes have “disproportionately large contributions” to global CO2 and CH4 emissions, with the team estimating that they are responsible for between 25 and 37 percent of emissions while only comprising 15 percent of the total area of lakes. Understanding the development and effect that such lakes have on the environment may be key to effectively combating GHG emissions originating from lakes.
The study’s authors have shared their findings with the United Nations (UN). Their new dataset could inform the decisions and policies formulated by the UN’s Intergovernmental Panel on Climate Change (IPCC). The IPCC may use the data in assessing flood risks and improving lake management guidelines, as well as factoring it into their calculations of global GHG emissions.