The COVID-19 has become a pandemic. The timing and nature of the COVID-19 pandemic response and control varied among the regions and from one country to the other, and their role in affecting the spread of the disease has been debated. The focus of this work is on the early phase of the disease when control measures can be most effective. We proposed a modified susceptible-exposed-infected-removed model (SEIR) model based on temporal moving windows to quantify COVID-19 transmission patterns and compare the temporal progress of disease spread in six representative regions worldwide: three Chinese regions (Zhejiang, Guangdong and Xinjiang) vs. three countries (South Korea, Italy and Iran). It was found that in the early phase of COVID-19 spread the disease follows a certain empirical law that is common in all regions considered. Simulations of the imposition of strong social distancing measures were used to evaluate the impact that these measures might have had on the duration and severity of COVID-19 outbreaks in the three countries. Measure-dependent transmission rates followed a modified normal distribution (empirical law) in the three Chinese regions. These rates responded quickly to the launch of the 1 st -level Response to Major Public Health Emergency in each region, peaking after 1–2 days, reaching their inflection points after 10–19 days, and dropping to zero after 11–18 days since the 1 st -level response was launched. By March 29 th , the mortality rates were 0.08% (Zhejiang), 0.54% (Guangdong) and 3.95% (Xinjiang). Subsequent modeling simulations were based on the working assumption that similar infection transmission control measures were taken in South Korea as in Zhejiang on February 25 th , in Italy as in Guangdong on February 25 th , and in Iran as in Xinjiang on March 8 th . The results showed that by June 15 th the accumulated infection cases could have been reduced by 32.49% (South Korea), 98.16% (Italy) and 85.73% (Iran). The surface air temperature showed stronger association with transmission rate of COVID-19 than surface relative humidity. On the basis of these findings, disease control measures were shown to be particularly effective in flattening and shrinking the COVID-10 case curve, which could effectively reduce the severity of the disease and mitigate medical burden. The proposed empirical law and the SEIR-temporal moving window model can also be used to study infectious disease outbreaks worldwide.

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Coastal saltmarshes are key ecosystems with important ecological functions. Yet, they have experienced widespread decline. Due to their importance, the conservation and restoration of saltmarshes are globally-shared objectives, including China. Despite multiple local studies, nationwide information about saltmarshes in China is scarce. Thus, we used remote sensing to delineate the spatial distribution and areal extent of saltmarshes along coastal China, and resolve their species composition. By interpreting 10 m spatial resolution Sentinel-2 images on Google Earth Engine, assisted with field survey and literature search, totally 118,010 ha of saltmarshes were delineated in coastal China in 2019. Seven typical saltmarsh species were identified, with Phragmites australis, Spartina alterniflora and Scirpus mariquater as dominant species, accounting for 95.5% of total saltmarsh extent, while Suaeda salsa, Tamarix chinensis, Cyperus malaccensis and Sesuvium portulacastrum were present in limited abundance. The P. australis and exotic species S. alterniflora grow along almost all coastal provinces, but P. australis dominates in the north while S. alterniflora dominates in the middle part of coastal China. Suaeda salsa occurs mainly in the north and has suffered large losses. Tamarix chinensis is abundant in Shandong province, S. mariquater in the Yangtze River delta, C. malaccensis in Guangdong and Guangxi provinces, and S. portulacastrum in Taiwan. The exotic species S. alterniflora expanded extensively along the coast and its expansion rate continues to increase. The results provided conform a muchneeded baseline for future monitoring efforts and the assessment of progress in the conservation and restoration projects toward recovering saltmarshes in China. Index Terms-Distribution, remote sensing, saltmarsh, Sentinel-2 I. INTRODUCTION ALTMARSHES are coastal ecosystems formed by herbaceous communities growing in saltwater or brackish mudflats that