Small artificial waterbodies are widespread and persistent emitters of methane and carbon dioxide

Abstract

This is an open access article under the terms of the Creat ive Commo ns Attri butio n-NonCo mmerc ial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.

Florida’s urban stormwater ponds are net sources of carbon to the atmosphere despite increased carbon burial over time

“…2). So, while primary production contributes to a decrease in CO 2 emissions, the increased pH can exert a compounding effect, rendering high pH ponds and lakes to be weak CO 2 sources, similar to observations in in other urban ponds 11 , saline lakes 33 , and in agricultural reservoirs 34 . Other abiotic factors may contribute to an increase in pH.…”

“…Despite this widespread presence, SWPs are overlooked and underresearched and little is known about their role in regional C cycling or their net benefit to society (services vs. disservices). Still, the growing body of research on artificial waters and urban ponds has shown that they are capable of emitting substantial quantities of carbon dioxide (CO 2 ) and methane (CH 4 ) greenhouse gases (GHGs) and potentially more so than natural ecosystems, up to 2.5x more compared to natural ponds <10,000 m 2 in area 11 , despite high C burial rates 12 .…”

“…Despite high rates of C accumulation in sediments, small ponds are typically net C sources, driven by CO 2 and CH 4 emission to the atmosphere. For example, in terms of CO 2 equivalents, 96% of artificial ponds and ditches from seven countries were net sources of GHGs to the atmosphere 11 . Similarly, an investigation of 77 small agricultural impoundments (Victoria, Australia) showed that they accounted for 3.4x higher CO 2 equivalent fluxes than temperate reservoirs while having only 0.94 times the comparative area 15 .…”

Fencing farm dams to exclude livestock halves methane emissions and improves water quality

“…Farm dams (or agricultural ponds) are small, human‐made freshwater bodies created for the purpose of storing water for livestock or crop irrigation (Malerba et al, 2022). These systems have some of the highest greenhouse gas (GHG) emissions per m 2 among freshwater ecosystems (Grinham et al, 2018; Ollivier et al, 2018, 2019) due to their much higher nitrogen and phosphorus concentrations than natural ponds (Westgate et al, 2022), creating the perfect conditions for methanogenesis and GHG emissions (Li et al, 2021; Panneer Selvam et al, 2014; Peacock et al, 2021). Importantly, eutrophication appears to have a disproportionate effect on farm dams.…”

ReaLSAT, a global dataset of reservoir and lake surface area variations

“…In limnology, the origin/type of lake is a very important regulator of ecosystem dynamics. For instance, reservoirs will have faster water flow and lower residence time than natural lakes, and therefore nutrient and carbon processing rates will differ 22 ; floodplain lakes may dry periodically, leading to the denudation of sediments and changing CO2 emissions 23 ; and artificially constructed waterbodies will likely have much higher rates of nutrient loading and methane production than natural lakes 24 . Hence, aggregating pixels to the level of unique ecological entities (e.g., lakes, reservoirs, farm ponds etc.)…”