Citation: Mondal, B.; Bauddh, K.; Kumar, A.; Bordoloi, N. India’s Contribution to Greenhouse Gas Emission from Freshwater Ecosystems: A Comprehensive Review. Water 2022, 14, 2965. https://doi.org/10.3390/ w14192965 Academic Editors: Qilin Wang, Guy Howard and Liudmila S. Shirokova Received: 19 August 2022 Accepted: 16 September 2022 Published: 21 September 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). water Review India’s Contribution to Greenhouse Gas Emission from Freshwater Ecosystems: A Comprehensive Review Bipradeep Mondal 1 , Kuldeep Bauddh 1 , Amit Kumar 2, * and Nirmali Bordoloi 1, * 1 Department of Environmental Sciences, School of Natural Resource Management, Central University of Jharkhand, Brambe, Ranchi 835205, India 2 School of Hydrology and Water Resources, Nanjing University of Information Science and Technology, Nanjing 210044, China * Correspondence: amitkdah@nuist.edu.cn (A.K.); nirmali.bordoloi@cuj.ac.in (N.B.) Abstract: In the modern era, due to urbanization, industrialization, and anthropogenic activities in the catchment, greenhouse gas (GHG; CO 2 , CH 4 , and N 2 O) emissions from freshwater ecosystems received scientific attention because of global warming and future climate impacts. A developing country such as India contributes a huge share (4% of global) of GHGs from its freshwater ecosystems (e.g., rivers, lakes, reservoirs) to the atmosphere. This is the first comprehensive review dealing with the GHG emissions from Indian freshwater bodies. Literature reveals that the majority of GHG from India is emitted from its inland water, with 19% of CH 4 flux and 56% of CO 2 flux. A large part of India’s gross domestic product (GDP) is manipulated by its rivers. As a matter of fact, 117.8 Tg CO 2 year −1 of CO 2 is released from its major riverine waters. The potential of GHG emissions from hydropower reservoirs varies between 11–52.9% (mainly CH 4 and CO 2 ) because of spatio-temporal variability in the GHG emissions. A significant contribution was also reported from urban lakes, wetlands, and other inland waters. Being a subtropical country, India is one of the global GHG hotspots, having the highest ratio (GHG: GDP) of 1301.79. However, a large portion of India’s freshwater has not been considered yet, and there is a need to account for precise regional carbon budgets. Therefore, in this review, GHG emissions from India’s freshwater bodies, drivers behind GHG emissions (e.g., pH, mean depth, dissolved oxygen, and nutrients), and long-term climatic risks are thoroughly reviewed. Besides research gaps, future directions and mitigation measures are being suggested to provide useful insight into the carbon dynamics (sink/source) and control of GHG emissions. Keywords: greenhouse gases; freshwater ecosystems; rivers; reservoirs; lakes 1. Introduction India is the 3rd highest emitter of greenhouse gases (GHGs) among the top ten emit- ting countries with the highest gross domestic production (GDP) worldwide [1]. Being a developing country, India is still in unprecedented progress toward the growth of its economy, urbanization, and industrialization. The increasing GHGs emission has simulta- neously amplified the consequences of global climate change. One of the most deliberate impacts of the increased concentration of GHGs (particularly CO 2 ) is the increase in mean global temperature. During the 20th century, the Earth’s average temperature increased by 0.6 ± 0.12 ◦ C and is expected to increase by 1.5–5.8 ◦ C by the end of the twenty-first century [2]. Perhaps, weather extremities such as cyclones, hurricanes, floods, and drought are more frequent. The sixth report of the IPCC has indicated that anthropogenic impacts are one of the major influences behind the acceleration of climate change and extreme events leading to sea level rise and snowcap melting [3]. Similar is the case of India, where IPCC [4] predicted that in the future, India would experience more weather extremities, such as heat waves, floods, cyclones, drought, etc. Studies have found that carbon dioxide Water 2022, 14, 2965. https://doi.org/10.3390/w14192965 https://www.mdpi.com/journal/water