Ecological Barrier Deterioration Driven by Human Activities Poses Fatal Threats to Public Health due to Emerging Infectious Diseases

The coronavirus disease 2019(COVID-19)and concerns about several other pandemics in the 21st century have attracted extensive global attention.These emerging infectious diseases threaten global public health and raise urgent studies on unraveling the underlying mechanisms of their transmission from animals to humans.Although numerous works have intensively discussed the cross-species and endemic barriers to the occurrence and spread of emerging infectious diseases,both types of barriers play synergistic roles in wildlife habitats.Thus far,there is still a lack of a complete understanding of viral diffusion,migration,and transmission in ecosystems from a macro perspective.In this review,we conceptualize the ecological barrier that represents the combined effects of cross-species and endemic barriers for either the natural or intermediate hosts of viruses.We comprehensively discuss the key influential factors affecting the ecological barrier against viral transmission from virus hosts in their natural habitats into human society,including transmission routes,contact probability,contact frequency,and viral characteristics.Considering the significant impacts of human activities and global industrialization on the strength of the ecological barrier,ecological barrier deterioration driven by human activities is critically analyzed for potential mechanisms.Global climate change can trigger and expand the range of emerging infectious diseases,and human disturbances promote higher contact frequency and greater transmission possibility.In addition,globalization drives more transmission routes and produces new high-risk regions in city areas.This review aims to provide a new concept for and comprehensive evidence of the ecological barrier blocking the transmission and spread of emerging infectious diseases.It also offers new insights into potential strategies to protect the ecological barrier and reduce the wide-ranging risks of emerging infectious diseases to public health.

Green Barriers： Obstacle or Stimulation ？

Most viewpoints in China consider green barrier is one kind of non-tariff barriers imposed by developed countries and is unfair to developing countries. Different from these, this paper points out that green barriers, evolving from the background of sustainable development theory and the principle of environment protection, have positive effect on ideology, international institutional arrangement and innovation stimulation. Demonstrating the rationality of green barriers, the paper puts forward that green barriers should be regarded as the stimulation for technology innovation and industrial restructure rather than obstacles. The best way to surmount the green barriers for Chinese government and enterprises is to implement circular economy and clean production so as to achieve the harmony of trade, environment and economic development.

Trans-Gulf of Mexico loop migration of tree swallows revealed by solar geolocation

One of the greatest feats of avian migration is the non-stop crossing of extensive areas of inhospitable habitat such as deserts and seas. Differences in spring and autumn migration routes have been reported in species that cross such barriers, and are thought to have evolved in response to seasonal variation in prevailing wind direction. We tested the hypothesis that migration routes vary seasonally with respect to the Gulf of Mexico in the tree swallow Tachycineta bicolor using solar geolocators attached and retrieved at 4 breeding sites in central North America. We found that 100 % of birds （n = 10） made a trans-Gulf flight of 〉850 km from Louisiana south to their wintering grounds in the Yucatan Peninsula in 12-36 hours, achieving minimum ground speeds as high as 32 m/s. Although most days during autumn migration were characterized by unfavorable headwinds blowing to the northwest, migration over the Gulf mostly occurred on days with strong winds blowing to the south. In contrast, in 8 of 9 （88 %） birds on spring migration returned from the wintering grounds towards Louisiana following a clockwise loop pat- tern flying over land to the west around the Gulf. During this spring period there were few days with prevailing winds from the south to assist northward migration. Results suggest that, despite being up to three times further （ca. 2,700 kin）, a coastal circum-Gulf spring migration represents the less risky route when wind conditions are not favorable. These findings also help to resolve a long-standing dispute in the literature concerning migration patterns between the US Gulf coast and Mexico, and provide insight into the factors shaping migration strategies of small songbirds migrating across large bodies of water [Current Zoology 60（5）： 653-559, 2014].

Research strategy for constructing a green infrastructure network based on spatial prioritization

The destruction of the ecological system caused by urban expansion has led to the environmental deterioration,cities have become increasingly vulnerable.In this study,six districts and counties along the Yellow River in Zhengzhou were selected as the study area.First,green infrastructure elements were extracted by morphological spatial pattern analysis.Then,outside the urban areas,we used connectivity analysis to evaluate the importance of core areas,adopted minimum cumulative resistance model to extract potential corridors,and identified the important corridors by using the gravity model.Finally,in the urban areas,we set up an evaluation system to assess the demands for ecosystem services.The results showed that:(1)Seven landscape types of green infrastructure be identified in study area.(2)There are 17 vital cores,136 potential corridors,and 24 vital corridors outside the urban areas.(3)The blocks with high demand for ecosystem services are mostly concentrated in the old blocks with dense populations and poor infrastructure,and there are 5 blocks with comprehensive high-demand.Based on identified importance for green infrastructure land space,and high-demand level for ecosystem services areas in this study,a green infrastructure net plan was proposed based on spatial conservation prioritisation.