Environmental impacts of the billion tree Tsunami project in Khyber Pakhtunkhwa on the dynamics of Agro-Meteorological Droughts

IF 5.9 1区地球科学 Q1 ENGINEERING, CIVIL

Journal of Hydrology Pub Date : 2024-10-22 DOI:10.1016/j.jhydrol.2024.132205

Khalil Ur Rahman , Deqiang Mao , Nuaman Ejaz , Quoc Bao Pham , Anwar Hussain , Meriame Mohajane , Muhammad Ali , Songhao Shang

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引用次数: 0

Abstract

Changes in forest cover are closely associated with the variability in meteorological and hydrological variables. Therefore, this study delves into investigating how forest cover changes impact the environment (i.e., hydro-meteorological variables, including precipitation, streamflow, relative humidity (RH), evapotranspiration (ET), and temperature) using Trend Projection (TP) methods during 1980–2019. The study is carried out in the Khyber Pakhtunkhwa (KP) province of Pakistan, which witnessed deforestation between 1980 and 2010 followed by afforestation (through billion tree tsunami project, BTTP) initiated in 2014. A new drought index, named as agro-meteorological drought index (AMDI), is developed in this study using the remotely sensed data to analyze the impact of forest cover on drought severity. The robust least square regression (RLSR) model is used to regress the normalized difference vegetation index (NDVI) with AMDI at various time scales to investigate the impact of forest cover on drought severity. The RLSR and paired t-test are used to quantify the impact of forest cover and BTTP, in particular, on the environment. Land use maps prepared for KP province over a span of the past four decades revealed significant deforestation during 1985–2005, transitioning gradually to afforestation in the past decade. Results indicated a decline in streamflow throughout different seasons with an increase in forest cover, particularly during the period of afforestation (i.e., 2015–2019). The precipitation, RH (maximum/minimum), and ET displayed an increasing trend over time, whereas a decrease trend is observed in Tmax/Tmin and streamflow at most of the stations. The trend analyses depicted a significant change before and after the BTTP. The paired t-test results revealed that BTTP has statistically significant impact on the environmental variables. Furthermore, the time series plots of AMDI at different time scales indicated that drought events were frequent and severe prior to 2003, whereas significant decrease in both the frequency and severity of drought was observed in the last decade (2010–2019). The RLSR results at pixel scales demonstrated the crucial role of forest covers in alleviating both the frequency and severity of drought events. The elasticities revealed that increase in the forest cover resulted in substantial increase/decrease in each hydro-meteorological variable. Overall, the results highlighted a positive and statistically significant impact of forest cover (i.e., BTTP) on both the environment and drought variability.

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开伯尔巴图克瓦省十亿棵树海啸项目对农业气象干旱动态的环境影响

森林覆盖率的变化与气象和水文变量的变化密切相关。因此，本研究采用趋势预测（TP）方法，深入研究 1980-2019 年间森林覆盖率的变化如何影响环境（即水文气象变量，包括降水、溪流、相对湿度（RH）、蒸散量（ET）和温度）。该研究在巴基斯坦开伯尔-普赫图赫瓦（KP）省进行，该省在 1980 年至 2010 年期间发生了森林砍伐，随后于 2014 年启动了植树造林（通过十亿棵树海啸项目，BTTP）。本研究利用遥感数据建立了一个新的干旱指数，命名为农业气象干旱指数（AMDI），以分析森林覆盖率对干旱严重程度的影响。采用稳健最小二乘法回归（RLSR）模型对归一化差异植被指数（NDVI）和 AMDI 在不同时间尺度上进行回归，以研究森林植被对干旱严重程度的影响。使用 RLSR 和配对 t 检验来量化森林覆盖率，特别是 BTTP 对环境的影响。过去 40 年间绘制的金沙萨省土地利用图显示，1985-2005 年期间森林砍伐严重，过去 10 年逐渐过渡到植树造林。结果表明，随着森林覆盖率的增加，不同季节的河水流量都有所下降，特别是在植树造林期间（即 2015-2019 年）。降水量、相对湿度（最大/最小）和蒸散发随着时间的推移呈上升趋势，而大多数站点的最高/最低温度和溪流则呈下降趋势。趋势分析表明，在 BTTP 实施前后出现了显著变化。配对 t 检验结果表明，BTTP 对环境变量的影响具有统计学意义。此外，不同时间尺度的 AMDI 时间序列图显示，2003 年之前干旱事件频繁发生且严重，而在过去十年（2010-2019 年）中，干旱的频率和严重程度均明显下降。像素尺度的 RLSR 结果表明，森林植被在缓解干旱事件的频率和严重程度方面发挥着至关重要的作用。弹性系数显示，森林覆盖率的增加导致每个水文气象变量的大幅增加/减少。总体而言，结果凸显了森林覆盖率（即 BTTP）对环境和干旱变异性的积极和统计意义上的影响。

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来源期刊

Journal of Hydrology 地学-地球科学综合

CiteScore

11.00

自引率

12.50%

发文量

1309

审稿时长

7.5 months

期刊介绍： The Journal of Hydrology publishes original research papers and comprehensive reviews in all the subfields of the hydrological sciences including water based management and policy issues that impact on economics and society. These comprise, but are not limited to the physical, chemical, biogeochemical, stochastic and systems aspects of surface and groundwater hydrology, hydrometeorology and hydrogeology. Relevant topics incorporating the insights and methodologies of disciplines such as climatology, water resource systems, hydraulics, agrohydrology, geomorphology, soil science, instrumentation and remote sensing, civil and environmental engineering are included. Social science perspectives on hydrological problems such as resource and ecological economics, environmental sociology, psychology and behavioural science, management and policy analysis are also invited. Multi-and interdisciplinary analyses of hydrological problems are within scope. The science published in the Journal of Hydrology is relevant to catchment scales rather than exclusively to a local scale or site.