Spatiotemporal behavior of floods and droughts and their impacts on agriculture in China

Highlights

• First attempt in addressing flood- and drought-induced agricultural loss

• Novel insight into flood- and drought-influenced crop areas

• Impacts of precipitation regimes and human mitigations are included.

• Provide solid evidence for diverse influences of floods and droughts on agriculture

Abstract

China is an agricultural country with the largest population in the world. However, intensification of droughts and floods and amplification of precipitation extremes are having critical negative impacts on agriculture. In this study, flood- and drought-affected, flood- and drought-damaged crop areas, and also flood- and drought-induced agricultural loss from 29 provinces across China are analyzed in both space and time. Results indicate the following: (1) Large parts of China are dominated by intensified floods. Comparatively, spatial ranges dominated by intensifying drought hazards are smaller than those by intensifying flood hazards. (2) Drought intensity is increasing in northwest China with moderate changes in the degree of influence. Increasing flood intensity can be observed in northwest, southwest and central China. However, flood risks are higher in arid regions such as northwest China and drought risks are higher in humid regions such as southwest China. (3) Agreements are identified between abrupt behaviors of flood-affected and -destroyed crop areas. The change points of flood-affected and -destroyed crop areas is in the 1980s in northeast, north and central China and in the 1990s in south and southwest China. Nevertheless, spatial patterns of the change points in the drought-affected and -destroyed crop areas are sporadic but not confirmative. (4) Flood- and drought-induced losses of agricultural production have significant increasing trends in most parts of China. The loss rate and loss magnitude of agriculture before change points are significantly higher than those after change points. (5) Generally, amplifications of precipitation extremes, decreasing consecutive wet days and increasing consecutive dry days in both space and time are the major driving factors behind the changes of drought- and flood-affected, and -destroyed crop areas and their impacts on agriculture across China. These results are theoretically and practically relevant for planning and management of agricultural activities and may help provide a theoretical framework for similar studies in other regions of the globe.

Introduction

Human-induced climate warming has been well evidenced and warming climate has the potential to accelerate the global- and continental-scale hydrological cycle (Alan et al., 2003, Zhang et al., 2013). Under the influence of warming climate, prime hydrological components, such as precipitation, are subject to alteration. Decreasing rainfall trend has been observed in the Mediterranean area (Karl, 1998) and significant decreasing trends in extreme rainfall have been observed in Western Australia (Haylock and Nicholls, 2000). However, an increasing trend in extreme precipitation was identified in the United States (e.g., Kunkel, 2003) and no trend in extreme rainfall was found in Canada (Zhang et al., 2001). Due to diverse underlying properties and various human activities, precipitation changes in China are varying significantly in both space and time (e.g. Wang and Zhou, 2005, Zhang et al., 2011a). Furthermore, spatiotemporal alterations of precipitation regimes due to warming climate and ENSO events evidently alter spatiotemporal patterns of floods and droughts (Zhang et al., 2011a, Zhang et al., 2013, Zhang et al., 2015). It should be noted that the rain-fed agriculture shoulders the largest burden of providing food in the developing countries (Sharma, 2011). Impacts of droughts, floods and precipitation changes on agriculture and hence the food security have been drawing increasing attention from academic communities in recent decades (Devereux, 2007, Douglas, 2009, Zhang et al., 2012a, Qin et al., 2014).

The human society faces diverse challenges to food security due to persistent population growth and rapid diet transition to decreasing cropland area and insufficient production practices (Beddington et al., 2012). Climate changes have the potential to exacerbate the already-fragile global food production system and the natural resource base (Ye et al., 2014). Global surface temperature has increased by 0.8 °C during the twentieth century; 3/4 of this increase occurred in the last three decades (Hansen et al., 2006, Ye et al., 2013, Ye et al., 2014). The acceleration in global warming and its associated changes in precipitation have already affected global agriculture and the food production system in many ways (Godfray et al., 2011, Ye et al., 2014). Due to catastrophic consequences of weather and hydrological extremes, such as floods, droughts, rainstorms, and heat waves and their negative effects on agricultural production, there have been a multitude of studies addressing agricultural loss as a result of agro-droughts and floods. Li et al. (2012) presented a preliminary methodology and an operational approach for assessing the risk of flood loss to the population, crops, housing, and the economy at the county level in China. Using a compatible crop model, Rosenzweig and Parry (1994) examined the potential impact of global change on food supply and price.

Agriculture is the major source of food and fiber, and it is particularly true for China. Besides, food security means a great deal for the stability of society in China. However, climate change adds a large degree of uncertainty to the projection of agricultural output, and food security will be the daunting challenge China will face. Therefore, it is important to evaluate spatiotemporal properties of droughts and floods in China and related impacts on agricultural production. Changes in precipitation and streamflow have been analyzed and their possible impacts on agriculture studied (Zhang et al., 2011b, Zhang et al., 2012a, Zhang et al., 2012b). Qin et al. (2014) quantitatively modeled the relationship between agro-drought and Chinese grain production. However, these studies did not address the abrupt behavior of flood and drought hazards and their impacts on agricultural production. Moreover, influences of floods and droughts on some specific agricultural production, such as rice, have not yet been investigated. Therefore, the objectives of this study are to: (1) investigate spatial patterns of drought- and flood-affected, and drought- and flood-destroyed crop areas, flood intensity and drought intensity and abrupt behaviors of flooding and drought regimes and their impacts on agricultural production, such as maize, rice and so on; and (2) analyze relations between occurrences of floods and droughts and loss of agricultural production. This study is of theoretical and practical merit in the management of agricultural activities and alleviation of negative effects of floods and droughts on agriculture in China.