The impact of intensification and deintensification of Asian rice production: transitions between wet and dry ecologies

水稻是世界上最重要的农作物之一，在东亚、南亚和东南亚，它有着悠久的支持密集人口和文明的历史。该项目将利用切割时代考古学来比较整个地区的水稻种植历史。一个主要目标是重建该地区不同时期的水稻种植方式。水稻可以在湿润栽培系统（灌溉或淹没）和干旱栽培（仅基于降雨，通常在高地地区）以及中间低地，干旱条件下种植。这些不同的系统对水稻的产量有重要影响，因此它可以支持多少人口，以及它的劳动密集程度。干式系统产量较低，但劳动力成本也较低。水稻的种植方式对人类和水稻对环境变化的影响具有重要意义。密集型系统往往需要更大的景观改造，并通过支持更多的人口对其他资源产生连锁反应，例如通过砍伐森林。另一个非常重要的影响是甲烷的产生，这是一种导致全球变暖的温室气体。旱稻种植系统产生的甲烷很少，而生产力更高的湿润系统产生大量甲烷。一些气候科学家假设，在过去的5000年里，水稻中的甲烷导致了甲烷的异常上升，这是无法用自然来源解释的。如果是这样的话，那么这甚至在工业时代之前就已经导致了全球变暖，并且需要将其纳入希望预测全球气候变化走向的模型中。该项目的目的之一是通过从水稻种植的经验考古证据中建模，以评估这是否适合解释甲烷异常的至少一部分，从而使这一假设成为事实。为了做到这一点，我们不仅需要更好的证据来证明水稻是在何时何地种植的，而且还需要证明它是在湿润或干燥的系统中种植的。通过对考古保存的种子的系统研究，我们可以确定与过去的水稻有关的杂草植物群，以及它是否适合潮湿或干燥系统。此外，我们已经开发出的组合的植硅体（微观硅从植物的分解）从考古遗址指示潮湿或干燥的水稻种植制度进行分类的方法。我们现在希望将这些方法应用于更多的地点和地区，特别是那些早稻考古植物学证据有限或缺乏的地区，包括印度（西部和东北部），孟加拉国，缅甸，柬埔寨，越南和中国南部（云南，四川，广东）。通过将这些新的结果结合到GIS建模系统中，再加上我们和同事们在过去几年中收集的该地区其他地区的数据，我们将能够更好地制作水稻传播的现实空间模型，湿稻的范围，以及可能的甲烷排放量。我们还将能够提高我们对水稻农业的发展如何与该地区人类社会的长期历史相关联的理解。

Rice is one of the worlds most important crops, and it has a long history of supporting dense populations and civilizations throughout East, South and Southeast Asia. This project will reveal the history of rice cultivation comparatively across the region using cutting age archaeological science. One major aim is to reconstruct how rice was grown across the region at different times. Rice may be grown in wet cultivation systems (irrigated or flooded) and dry cultivation (based only on rainfall, often in upland areas), and in intermediate lowland, rainfed conditions. These different systems have important implications in terms of how productive rice is, and therefore how much human population it can support, as well as how labour-intensive it was. Dry systems yielded less but also cost less in terms of labour. How rice was grown has important implications for the impact that humans and rice had on environmental change. Intensive systems tend to require greater landscape modification and by supporting higher populations have knock-on effects on other resources, for example through deforestation. Another very important impact is the production of methane, a greenhouse gas that contributes to global warming. Dry rice cultivation systems produce little methane whereas the more productive wet systems produce a lot. It has been hypothesized by some climate scientists that methane from rice contributed to an anomalous rise in methane over the past 5000 years which is not explained by natural sources. If so, then this has contributed to global warming even before the industrial era and will need to be factored into models that hope to predict where global climate change is going. One of the aims of this project is to ground truth this hypothesis by modelling up from the empirical archaeological evidence for rice cultivation over time to assess whether this fits with explaining at least part of the methane anomaly. In order to do this we need better evidence not just for where and when rice was cultivated but also whether it was grown in wet or dry systems. Through systematic study of archaeologically preserved seeds, we can identify the weed flora associated with past rice and whether it fits with a wet or dry system. In addition we have developed methods for classifying the assemblages of phytoliths (microscopic silica from the decomposition of plants) from archaeological sites as indicating wetter or drier rice cultivation regimes. We are now hoping to apply these methods over a larger number of sites and regions, especially regions for which archaeobotanical evidence for early rice is limited or lacking, including parts of India (western and northeastern), Bangladesh, Myanmar, Cambodia, Vietnam, and southern China (Yunnan, Sichuan, Guangdong). By combining these new results in a GIS modelling system, together with data from other parts of the region, mostly collected by us and colleagues over the past few years, we will be better able to produce realistic spatial models of the spread of rice, the extent of wet rice, and likely methane emissions over time. We will also be able to improve our understanding of how the development of rice agriculture relates to the long-term history of human societies in this region.