Background: A number of conservation and societal issues require understanding how species are distributed on the landscape, yet ecologists are often faced with a lack of data to develop models at the resolution and e...Background: A number of conservation and societal issues require understanding how species are distributed on the landscape, yet ecologists are often faced with a lack of data to develop models at the resolution and extent desired, resulting in inefficient use of conservation resources.Such a situation presented itself in our attempt to develop waterfowl distribution models as part of a multi-disciplinary team targeting the control of the highly pathogenic H5N1 avian influenza virus in China.Methods: Faced with limited data, we built species distribution models using a habitat suitability approach for China's breeding and non-breeding(hereafter, wintering) waterfowl.An extensive review of the literature was used to determine model parameters for habitat modeling.Habitat relationships were implemented in GIS using land cover covariates.Wintering models were validated using waterfowl census data, while breeding models, though developed for many species, were only validated for the one species with sufficient telemetry data available.Results: We developed suitability models for 42 waterfowl species(30 breeding and 39 wintering) at 1 km resolution for the extent of China, along with cumulative and genus level species richness maps.Breeding season models showed highest waterfowl suitability in wetlands of the high-elevation west-central plateau and northeastern China.Wintering waterfowl suitability was highest in the lowland regions of southeastern China.Validation measures indicated strong performance in predicting species presence.Comparing our model outputs to China's protected areas indicated that breeding habitat was generally better covered than wintering habitat, and identified locations for which additional research and protection should be prioritized.Conclusions: These suitability models are the first available for many of China's waterfowl species, and have direct utility to conservation and habitat planning and prioritizing management of critically important areas, providing an example of how this approach may aid others faced with the challenge of addressing conservation issues with little data to inform decision making.展开更多
The paper aims at proffering a solution for college English who experience a dilemma that they cannot tap their potential fully to improve the effectiveness and efficiency of writing in English. The author recommends ...The paper aims at proffering a solution for college English who experience a dilemma that they cannot tap their potential fully to improve the effectiveness and efficiency of writing in English. The author recommends model thinking which entails habitual application of models and thus formulating a kind of efficient thinking in composing and arranging the existent linguistic and disciplinary resources established in the students' mind as an approach for those students to further their English writing skills.展开更多
Every year billions of chickens are shipped thousands of miles around the globe in order to meet the ever increasing demands for this cheap and nutritious protein source.Unfortunately,transporting chickens internation...Every year billions of chickens are shipped thousands of miles around the globe in order to meet the ever increasing demands for this cheap and nutritious protein source.Unfortunately,transporting chickens internationally can also increase the chance for introducing zoonotic viruses,such as highly pathogenic avian influenza A(H5N1)to new countries.Our study used a retrospective analysis of poultry trading data from 2003 through 2011 to assess the risk of H5N1 poultry infection in an importing country.We found that the risk of infection in an importing country increased by a factor of 1.3(95%CI:1.1e1.5)for every 10-fold increase in live chickens imported from countries experiencing at least one H5N1 poultry case during that year.These results suggest that the risk in a particular country can be significantly reduced if imports from countries experiencing an outbreak are decreased during the year of infection or if biosecurity measures such as screening,vaccination,and infection control practices are increased.These findings show that limiting trade of live chickens or increasing infection control practices during contagious periods may be an important step in reducing the spread of H5N1 and other emerging avian influenza viruses.展开更多
Highly pathogenic avian influenza(HPAI)H5N1 continues to threaten domestic and wild birds,as well as human health.However,the mechanism of spatial transmission of HPAI is still unclear.We analyzed the current distribu...Highly pathogenic avian influenza(HPAI)H5N1 continues to threaten domestic and wild birds,as well as human health.However,the mechanism of spatial transmission of HPAI is still unclear.We analyzed the current distribu-tion of HPAI occurrences based on World Organization for Animal Health reported data from 3049 sites in the world from December 2003 to June 2006,and found that these sites were spaced at distances with a frequency peak of 100–200 km.We built a cellular automata model to simulate the spatial transmission process of HPAI as a function of transmission distance,variance of the transmission distance,infection rate,and transmission times(how many times HPAI transmits from one host to another before suppression).We determined that the transmis-sion distance between HPAI occurrences is approximately 100 km on the basis of historical HPAI occurrences from 2003 to 2006 in both wild and domestic birds.To effectively reduce the long-distance spreading of HPAI,preventing close contact between domestic birds and waterfowl within a radius of 100 km around HPAI occur-rence sites is essential.展开更多
基金supported by the United States Geological Survey(Ecosystems Mission Area)the National Science Foundation Small Grants for Exploratory Research(No.0713027)Wetlands International
文摘Background: A number of conservation and societal issues require understanding how species are distributed on the landscape, yet ecologists are often faced with a lack of data to develop models at the resolution and extent desired, resulting in inefficient use of conservation resources.Such a situation presented itself in our attempt to develop waterfowl distribution models as part of a multi-disciplinary team targeting the control of the highly pathogenic H5N1 avian influenza virus in China.Methods: Faced with limited data, we built species distribution models using a habitat suitability approach for China's breeding and non-breeding(hereafter, wintering) waterfowl.An extensive review of the literature was used to determine model parameters for habitat modeling.Habitat relationships were implemented in GIS using land cover covariates.Wintering models were validated using waterfowl census data, while breeding models, though developed for many species, were only validated for the one species with sufficient telemetry data available.Results: We developed suitability models for 42 waterfowl species(30 breeding and 39 wintering) at 1 km resolution for the extent of China, along with cumulative and genus level species richness maps.Breeding season models showed highest waterfowl suitability in wetlands of the high-elevation west-central plateau and northeastern China.Wintering waterfowl suitability was highest in the lowland regions of southeastern China.Validation measures indicated strong performance in predicting species presence.Comparing our model outputs to China's protected areas indicated that breeding habitat was generally better covered than wintering habitat, and identified locations for which additional research and protection should be prioritized.Conclusions: These suitability models are the first available for many of China's waterfowl species, and have direct utility to conservation and habitat planning and prioritizing management of critically important areas, providing an example of how this approach may aid others faced with the challenge of addressing conservation issues with little data to inform decision making.
文摘The paper aims at proffering a solution for college English who experience a dilemma that they cannot tap their potential fully to improve the effectiveness and efficiency of writing in English. The author recommends model thinking which entails habitual application of models and thus formulating a kind of efficient thinking in composing and arranging the existent linguistic and disciplinary resources established in the students' mind as an approach for those students to further their English writing skills.
基金This work is sponsored in part by the Robert Wood Johnson Foundation Pioneer Grant 67919.
文摘Every year billions of chickens are shipped thousands of miles around the globe in order to meet the ever increasing demands for this cheap and nutritious protein source.Unfortunately,transporting chickens internationally can also increase the chance for introducing zoonotic viruses,such as highly pathogenic avian influenza A(H5N1)to new countries.Our study used a retrospective analysis of poultry trading data from 2003 through 2011 to assess the risk of H5N1 poultry infection in an importing country.We found that the risk of infection in an importing country increased by a factor of 1.3(95%CI:1.1e1.5)for every 10-fold increase in live chickens imported from countries experiencing at least one H5N1 poultry case during that year.These results suggest that the risk in a particular country can be significantly reduced if imports from countries experiencing an outbreak are decreased during the year of infection or if biosecurity measures such as screening,vaccination,and infection control practices are increased.These findings show that limiting trade of live chickens or increasing infection control practices during contagious periods may be an important step in reducing the spread of H5N1 and other emerging avian influenza viruses.
文摘Highly pathogenic avian influenza(HPAI)H5N1 continues to threaten domestic and wild birds,as well as human health.However,the mechanism of spatial transmission of HPAI is still unclear.We analyzed the current distribu-tion of HPAI occurrences based on World Organization for Animal Health reported data from 3049 sites in the world from December 2003 to June 2006,and found that these sites were spaced at distances with a frequency peak of 100–200 km.We built a cellular automata model to simulate the spatial transmission process of HPAI as a function of transmission distance,variance of the transmission distance,infection rate,and transmission times(how many times HPAI transmits from one host to another before suppression).We determined that the transmis-sion distance between HPAI occurrences is approximately 100 km on the basis of historical HPAI occurrences from 2003 to 2006 in both wild and domestic birds.To effectively reduce the long-distance spreading of HPAI,preventing close contact between domestic birds and waterfowl within a radius of 100 km around HPAI occur-rence sites is essential.
