An international proposal with ground breaking, long-term importance, the Silk Road Economic Belt and the 21stCentury Maritime Silk Road (abbreviated "the Belt and Road") Initiative, is being advanced by China in response to the world's new development patterns in theW 21st century. It concerns China's future development over a long period of time and benefits people across the world. Featuring wide-ranging, diverse fields, it is a time-consuming, complicated and arduous systems engineering project and will face numerous difficulties and challenges.

Against the background of building a community with ashared future for mankind, China is making a rapid transition from a big country to a strong country, and shouldering even more global responsibilities. This requires our country to consolidate, step by step, its philosophy and scheme for opening to the outside world to improving global governance. Over the three years since the Initiative was launched, steady achievements have been made to bring the blueprint into reality.

As a national center for scientific research, the Chinese Academy of Sciences (CAS) has a grave responsibility to implement the Belt and Road Initiative and is duty-bound to lay a solid S & T foundation for the Initiative. Comprising a comprehensive and interdisciplinary research and development network, CAS enjoys a unique advantage in serving the Initiative with science and technology, especially space-based observation for Earth. In this respect, it has been playing an important part in the following three areas.

Facilitating inter-governmental collaboration through international S & T cooperation. In 2016, CAS held the First International Forum of National Scientific Organizations on the Belt and Road Initiative. Earlier, the International Symposium on Earth Observation for the Maritime Silk Road (EMSR) and the International Symposium on Earth Observation for One Belt and One Road (EOBAR) were convened. More than 1, 000 experts from over 50 countries made suggestions for the Belt and Road Initiative at the meetings. Although there is a great difference among countries along the Belt and Road in terms of natural environment, social policy, economy and culture, all of them face complicated challenges to sustainable development. As a major driving force for socioeconomic progress, S & T innovation will be the "golden key" to address complicated problems and challenges, and an"accelerator" to upgrade the infrastructures, transportation, trade and cultural exchanges among the countries.

Safeguarding the sustainable development of the Belt and Road Initiative through innovative applications of big data. The Digital Belt and Road (DBAR) Initiative launched by CAS scientists has received support from over 20 international organizations, such as the International Council for Science (ICSU) and the United Nations Educational, Scientific and Cultural Organization (UNESCO), and countries such as Finland, Russia, Kazakhstan, Kyrgyzstan, Cambodia and Sri Lanka. It is designed to swiftly provide a more accurate and extensive understanding of the Belt and Road through innovative international S & T cooperation on Earth observation, and to promote the development of big Earth data for the Belt and Road to support innovation in decision-making regarding such important areas as climate change, urban development, world heritage, natural disasters, food securityand water resources. A scientific community with a shared future along the Belt and Road will be built by establishing a big data platform, exchanging information products and technological services, and integrating ground-based and space-based Earth observation networks.

Expanding the visual field of space-borne observation of the Belt and Road region, Asia, Africa and Europe. The North Polar Ground Station of the CAS Institute of Remote Sensing and Digital Earth started operation in December 2016. As China's first land satellite ground receiving station constructed overseas, it has greatly improved China's capacity for global data acquisition. By 2020, China will have built advanced Earth observation systems for land, ocean and atmosphere, giving support and services to decision-making in modern agriculture, disaster mitigation and prevention, resources and environment, and public security, and ensuring the autonomy of information sources. While building a Green Belt and Road, a Digital Belt and Road, and a Friendship Belt and Road, we need to address numerous challenges regarding its environment, resources and disasters. It is important to have a comprehensive understanding of these issues and evaluate them in a scientific way. Space science and technology, including obtaining data in a macroscopic, accurate, objective manner, will support the Belt and Road Initiative from different perspectives.

Based on DBAR, this special issue, Safeguarding the Belt and Road with Space Science and Technology, will comprehensively highlight the capacity and role of space technology in supporting the Initiative. The DBAR will provide strong support for sustainable development along the Belt and Road and make sustained, high-level contributions to the Initiative.