Relative contributions of climate change, stomatal closure, and leaf area index changes to 20th and 21st century runoff change: A modelling approach using the Organizing Carbon and Hydrology in Dynamic Ecosystems (ORCHIDEE) land surface model

143

104

Abstract. This review summarizes the impacts of climate change on runoff in West Africa, assesses the uncertainty in the projections and describes future research needs for the region. To do so, we constitute a meta-database made of 19 studies and 301 future runoff change values. The future tendency in streamflow developments is overall very uncertain (median of the 301 points is 0 % and mean +5.2 %), except for (i) the Gambia River, which exhibits a significant negative change (median = −4.5 %), and (ii) the Sassandra and the Niger rivers, where the change is positive (+14.4 % and +6.1 %). A correlation analysis revealed that runoff changes are tightly linked to changes in rainfall (R = 0.49), and to a smaller extent also to changes in potential evapotranspiration. Other parameters than climate -such as the carbon effect on plant water efficiency, land use dynamics or water withdrawals -could also significantly impact on runoff, but they generally do not offset the effects of climate change. In view of the potential changes, the large uncertainty therein and the high vulnerability of the region to such changes, there is an urgent need for integrated studies that quantify the potential effects of these processes on water resources in West Africa and for more accuracy in climate models rainfall projections. We especially underline the lack of information concerning projections of future floods and droughts, and of interannual fluctuations in streamflow.

Section: Carbon Effect On Plant Water Usementioning

confidence: 99%

Climate change impacts on runoff in West Africa: a review

Roudier

Ducharne

Feyen

2014

143

104

“…The factor separation methodology from Stein and Alpert (1993) and Alkama et al (2010) is used to categorize the contributions of climate change, CO 2 fertilization, and LAI, as well as their interactions to long-term trends of ET and GPP. Similar to Alkama et al (2010), the total effect, f 123 , is expressed as…”

Section: Separation Of Climate Change and Management Effectsmentioning

confidence: 99%

“…Climate change dominated the interannual variability of ET, while land use changes and agricultural practices and techniques exerted more discernable effects on the water cycle in the long term . However, Alkama et al (2010) and Shi et al (2011) demonstrate that climate change is the predominant driver of the global ET tendency in the 20th century. Commonly, the contributions of climate change to vegetation productivities on a large scale are quantified by the ecosystem models or statistical models.…”

Section: Introductionmentioning

confidence: 99%

“…Separating the contributions of climatic change, CO 2 enrichment, and human activities to the long-term trends of water and carbon cycles is critical for assessment of ecosystem responses and resilience to environmental changes. Some researchers have explored the relative contributions of climate change and vegetation dynamics to changes in global land surface evapotranspiration and river runoff (Betts et al, 2007;Piao et al, 2007;Alkama et al, 2010;Liu et al, 2012;Chen et al, 2014Chen et al, , 2015Banger et al, 2015), but the conclusions are still inconsistent. Climate change dominated the interannual variability of ET, while land use changes and agricultural practices and techniques exerted more discernable effects on the water cycle in the long term .…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Attributing regional trends of evapotranspiration and gross primary productivity with remote sensing: a case study in the North China Plain

Chen

et al. 2017

Abstract. Attributing changes in evapotranspiration (ET) and gross primary productivity (GPP) is crucial for impact and adaptation assessment of the agro-ecosystems to climate change. Simulations with the VIP model revealed that annual ET and GPP slightly increased from 1981 to 2013 over the North China Plain. The tendencies of both ET and GPP were upward in the spring season, while they were weak and downward in the summer season. A complete factor analysis illustrated that the relative contributions of climatic change, CO 2 fertilization, and management to the ET (GPP) trend were 56 (−32) %, −28 (25) %, and 68 (108) %, respectively. The decline of global radiation resulted from deteriorated aerosol and air pollution was the principal cause of GPP decline in summer, while air warming intensified the water cycle and advanced the plant productivity in the spring season. Generally, agronomic improvements were the principal drivers of crop productivity enhancement.

“…Dai et al, 2009;Alkama et al, 2010Alkama et al, , 2011, it appears that the precise contribution of natural vs. anthropogenic drivers, and of changes in vegetation, to variations and trends in global discharge currently cannot be quantified on solid grounds. Even the existence of an upward global trend is hardly detectable with confidence.…”

Section: Effects Of Land Cover and Land Use Changes In The Global Watmentioning

confidence: 99%

A vital link: water and vegetation in the Anthropocene

Gerten

2013

Abstract. This paper argues that the interplay of water, carbon and vegetation dynamics fundamentally links some global trends in the current and conceivable future Anthropocene, such as cropland expansion, freshwater use, and climate change and its impacts. Based on a review of recent literature including geographically explicit simulation studies with the process-based LPJmL global biosphere model, it demonstrates that the connectivity of water and vegetation dynamics is vital for water security, food security and (terrestrial) ecosystem dynamics alike. The water limitation of net primary production of both natural and agricultural plantsalready pronounced in many regions -is shown to increase in many places under projected climate change, though this development is partially offset by water-saving direct CO 2 effects. Natural vegetation can to some degree adapt dynamically to higher water limitation, but agricultural crops usually require some form of active management to overcome it -among them irrigation, soil conservation and eventually shifts of cropland to areas that are less water-limited due to more favourable climatic conditions. While crucial to secure food production for a growing world population, such human interventions in water-vegetation systems have, as also shown, repercussions on the water cycle. Indeed, land use changes are shown to be the second-most important influence on the terrestrial water balance in recent times. Furthermore, climate change (warming and precipitation changes) will in many regions increase irrigation demand and decrease water availability, impeding rainfed and irrigated food production (if not CO 2 effects counterbalance this impact -which is unlikely at least in poorly managed systems). Drawing from these exemplary investigations, some research perspectives on how to further improve our knowledge of human-watervegetation interactions in the Anthropocene are outlined.