Satellite remote sensing of grasslands:from observation to management

Aims Grasslands are the world’s most extensive terrestrial ecosystem,and are a major feed source for livestock.Meeting increasing demand for meat and other dairy products in a sustainable manner is a big challenge.At a field scale,Global Positioning System and ground-based sensor technologies provide promising tools for grassland and herd management with high precision.With the growth in availability of spaceborne remote sensing data,it is therefore important to revisit the relevant methods and applications that can exploit this imagery.In this article,we have reviewed the(i)current status of grassland monitoring/observation methods and applications based on satellite remote sensing data,(ii)the technological and methodological developments to retrieve different grassland biophysical parameters and management characteristics(i.e.degradation,grazing intensity)and(iii)identified the key remaining challenges and some new upcoming trends for future development.Important Findings The retrieval of grassland biophysical parameters have evolved in recent years from classical regression analysis to more complex,efficient and robust modeling approaches,driven by satellite data,and are likely to continue to be the most robust method for deriving grassland information,however these require more high quality calibration and validation data.We found that the hypertemporal satellite data are widely used for time series generation,and particularly to overcome cloud contamination issues,but the current low spatial resolution of these instruments precludes their use for field-scale application in many countries.This trend may change with the current rise in launch of satellite constellations,such as RapidEye,Sentinel-2 and even the microsatellites such as those operated by Skybox Imaging.Microwave imagery has not been widely used for grassland applications,and a better understanding of the backscatter behaviour from different phenological stages is needed for more reliable products in cloudy regions.The development of hyperspectral satellite instrumentation and analytical methods will help for more detailed discrimination of habitat types,and the development of tools for greater end-user operation.

Allocation of grassland, livestock and arable based on the spatial and temporal analysis for food demand in China

To explore the distribution of food demand and the projected trend in future food demand in China, this paper analyzed the change in current(1998–2012) percapita demand for grain, grain-consuming and herbivorous livestock products, and predicted the food demand in 2020 The results indicated that in 1998–2012, the national percapita consumption of grain ration declined by about36.66%, and the per-capita consumption of grain-consuming and herbivorous livestock products increased by about 48% and 34.09%, respectively. The grain-consuming livestock products have become the primary source of both calories and protein for consumers. The proportion of herbivorous livestock products in consumer diets has increased steadily and there has been huge potential in substituting beef and mutton for pork in this dynamic market. The demand for food in different regions of China is highly variable, which is important for planning grassland agriculture development and ensuring food safety. The demand for grain, and grain-consuming and herbivorous livestock products will increase by about3.3%, 20% and 14% respectively by 2020. Based on the food demand and trend in the development of grassland agriculture, the 31 regions in China are divided into three priority groups for grassland agriculture development.

China’s new problems of food security revealed by the Food Equivalent Unit

China's food security has a great influence on the world,and has always been the top priority in China.In recent years,as the concept of food security is evolving into one of nutrition security and the importance of food diversity is increasing,research based on nutrition security and broad food systems are increasingly needed in today’s China.Thus,not only grain for human consumption,but also animal foods have been integrated into the Food Equivalent,which is used to analyze China’s current agriculture system and reveal the water resource distribution.The results indicated that the average animal food consumption has risen by 78.6%,and now China’s daily supply of animal food per capita has reached about 50%of that in the USA and 80%of that in the South Korea.So there exist an obvious disparity in animal food supply between China and these two countries.It is impossible for the China’s current agricultural system to achieve the level in the USA.Under China’s current agricultural system,the consumption proportion of feed grain had surpassed the consumption of food grain,increased sharply from 33%in 1992 to 67%in 2011.However,the growth potential of total grain output is approaching an upper limit,so the continued growth of feed grain demand exerts great pressure on the China’s food supply.The discordance of the spatial distribution of water resource and virtual water revealed that China’s current agriculture system had a low efficiency in being able to achieve food and nutrition security.China’s current“grain farming”cannot meet the demand of increasing nutrition and appropriate resource utilization.The implementation of grassland agriculture appears feasible and necessary for saving feed grain,providing a large number of high-quality animal foods and appropriate water resource utilization.