Climate Change Research ›› 2020, Vol. 16 ›› Issue (2): 182-193.

• New Scientific Understanding on Changes and Impacts of Oceans and Cryosphere •

### Impacts and risks of changing ocean on marine ecosystems and dependent communities and related responses

CAI Rong-Shuo1,HAN Zhi-Qiang2,YANG Zheng-Xian3

1. 1 Third Institute of Oceanography, Ministry of Natural Resources, Xiamen 361005, China
2 Zhejiang Ocean University, Zhoushan 316022, China
3 National Marine Environment Monitor Center, Dalian 116023, China
• Received:2020-02-18 Revised:2020-03-01 Online:2020-03-30 Published:2020-04-01

Abstract:

The IPCC special report on the ocean and cryosphere in a changing climate (SROCC) presents an assessment of the changes in the ocean climate, their impacts on ecosystems and human society, related risks, and responses. The results show that the physical and chemical properties of the ocean, such as warming, acidification, deoxygenation, and reduction of nutrients referred to ocean climate hazards, have changed significantly over the past decades (high confidence). This is affecting the marine ecosystems from the surface to sea floor and having negative consequences on human society and sustainable development (high confidence), e.g., the changes in biogeography of organisms ranging from phytoplankton to benthonic organism, consequently reduction in primary production and maximum catch potential of fish stocks as well as food provision etc. It is obvious that, globally, almost all marine ecosystems are expected to be at high or very high risk by the end of the 21st century under compound impacts of climate change and non-climatic anthropogenic factors, with increasing greenhouse gas emission (from RCP2.6 to RCP8.5 scenario) (high confidence). In particular, the warm water coral reefs are projected to disappear by 70%-90% and larger than 99% at global warming of 1.5℃ and 2℃, respectively (very high confidence). However, the effectiveness of many ocean-based climate mitigation is smaller or have higher uncertainties, and the capacity of many adaptation approaches for risk reduction, especially under the RCP8.5 scenario, are also limited. It is noted that RCP2.6 has a lower level of risk for all types of marine ecosystems than RCP8.5 (very high confidence). These highlight the critical importance of mitigation and the increasing effectiveness of the different type portfolios of mitigation and adaptation to climate change.