Green communications are focused on reducing energy consumption and making efficient use of resources to limit the impact on the planet. The European Union aims at reducing greenhouse gas emissions in 2030 by at least 50% compared with the year 1990. Communication systems are part of the problem as they contribute to greenhouse gas emissions, pollution, and climate change. For Wireless Sensor Networks (WSNs), the strategy to reduce energy is not clear as its performance and design are decided on a case-by-case basis. For some applications the system lifetime is crucial, while for others the event detection probability, packet delay, or coverage is more important. Additionally, the configuration, architecture, communication schemes, available resources, and type of monitoring among other factors have a direct impact on the energy consumption and quality of service (QoS) provided. As such, reducing energy consumption to reduce the impact on the planet is a challenging task. With the rise of the Internet of Things (IoT), we expect a massive deployment of nodes that may cause irreparable damage to the planet if these issues are not considered in the design of WSNs.

The use of organic and compostable materials is essential to provide harmless monitoring. Additionally, WSNs can be deployed to stimulate efficient energy use across different human and economic activities. For example, WSNs can be deployed to monitor pollution levels and vehicular traffic in smart city environments, reporting timely to users in order to encourage the use of clean energy means of transportation such as bikes or walking when possible. Furthermore, WSNs can be deployed to reduce water consumption and the use of fertilizers and insecticides by targeting specific zones while operating with low energy levels by means of research on node positioning and drone assisted WSNs, among others.

In this Special Issue, we welcome original research that aims at reducing the impact of WSNs on the environment by reducing energy consumption, not only to increase the system lifetime but also to make efficient use of resources to only use energy when needed, reducing carbon emissions and pollution. We especially welcome submissions providing innovative and multidisciplinary works ranging from materials, machine learning, communication networks, multivariable optimization, and others mainly aimed at reducing the impact of this monitoring technology deployment in the environment, including forests, parks, oceans, rivers, and other fragile ecosystems. We also hope to attract review articles that describe the current state of the art in this area.

Potential topics include but are not limited to the following:

• Low energy consumption WSNs
• Efficient resource utilization
• UAV assisted WSNs to reduce energy consumption
• Energy harvesting in WSNs
• Machine learning schemes to reduce energy consumption
• Clustering/data fusion/compression in WSNs to reduce energy consumption
• Mobile robot-assisted WSNs to reduce energy consumption
• Multivariable optimization for multiple QoS providing in resource-limited WSNs
• Organic and/or recyclable materials for node construction or batteries
• Use of clean energies in WSNs