Reforestation – climate change and water resource implications

Abstract

In a forested catchment, river discharge in any season can be either decreased or augmented by forest management practices such as appropriate species selection, density management, and length of rotation. The efficacy of any such strategy in either new plantations or existing forests can be maximized by considering the distribution of the key hydrological functions in the catchment. With the growing awareness of climate change and its impacts, the adequacy of our water supply is becoming an issue of increasing societal importance. At the same time there is greater discussion about using our forests for carbon sequestration and biofuels. Policy-makers should be careful when introducing new programs that incentivize widespread reforestation. The implications of such planting programs on annual and seasonal river flows (under both current and future climatic conditions) need to be considered. Informed choices need to be made as to the objectives for which we manage our forests. In turn, this means that there is an urgent need for water managers and forest managers to work more closely together than in the past to optimally plan and develop forest and water management strategies.Keywords: managing river flows by managing forests; modifying seasonal river flows; managing forests for energy or water yield; problems with incenting new planting programs; forests, water, and climate change RésuméDans un basin versant forestier, le débit d'un cours d' eau peut soit augmenter, soit diminuer en fonction des pratiques d'aménagement forestier comme la sélection appropriée des espèces, l'intensité de l'aménagement et la durée de la rotation. L' efficacité d'une telle stratégie pour de nouvelles plantations ou des peuplements existants peut être maximisée par l' étude de la distribution des principales fonctions hydrologiques du bassin versant. Compte tenu de l'accroissement de la sensibilisation face aux changements climatiques et à leurs conséquences, le niveau d'approvisionnement en eau est devenu un enjeu ayant une importance sociétale croissante. Au même moment, on discute de plus en plus de l'utilisation de nos forêts pour la sé-questration du carbone et la production de biocarburants. Les décideurs politiques doivent être prudents lorsque de nouveaux programmes sont introduits pour stimuler le reboisement à grande échelle. Les implications de ces programmes de reboisement sur le débit annuel des cours d' eau (en fonction des conditions climatiques actuelles et futures) doivent être étudiées. Des choix judicieux doivent être faits en fonction des objectifs pour lesquels nous aménageons nos forêts. En conséquence, cela signifie qu'il est urgent que les gestionnaires des eaux et les aménagistes forestiers collaborent plus étroitement que par le passé afin d' établir une planification optimale et de développer des stratégies adéquates d'aménagement des forêts et des eaux.Mots clés : gestion du débit des cours d' eau par l'aménagement des forêts; modification des débits saisonniers des cours d' eau; aménager les forê...

Partial river flow recovery with forest age is rare in the decades following establishment

“…Conversely, many would consider a reduction in annual river flow part of an effective environmental restoration programme to achieve historic conditions (Hjältén, Nilsson, Jørgensen, & Bell, ; Sterba, Mekotova, Krskova, Samsonova, & Harper, ), though determining whether reduced river flows are reflective of historical conditions is beyond the scope of this review. Rather than assert whether changes in river flow resulting from forestation would constitute an ecosystem service or disservice overall, we emphasize the potential importance of accounting for these changes in future forestation programmes so that forests may be accurately valued, to the benefit of local communities (Egginton et al, ). Whilst we found limited evidence for partial river flow recovery with forest age, we found that forestation on agricultural land results in a smaller reduction in river flow than on idle land, likely as a result of increased infiltration rates.…”

“…Rather than assert whether changes in river flow resulting from forestation would constitute an ecosystem service or disservice overall, we emphasize the potential importance of accounting for these changes in future forestation programmes so that forests may be accurately valued, to the benefit of local communities (Egginton et al, 2014). Whilst we found limited evidence for partial river flow recovery with forest age, we found that forestation on agricultural land results in a smaller reduction in river flow than on idle land, likely as a result of increased infiltration rates.…”

“…It is recognized that whether a decrease in river flow constitutes an ecosystem service or disservice is context specific (Dittrich, Ball, Wreford, Moran, & Spray, 2018;Dymond et al, 2012). However, significant questions remain regarding long-term trends in river flow response to forestation, and how responses will be affected by an increasingly variable climate (Blöschl et al, 2007;Egginton, Beall, & Buttle, 2014;Locatelli & Vignola, 2009;Yan et al, 2019). Although spontaneous forest regeneration may be key to facilitating large increases in forest cover (Yu et al, 2019), considerably less is known about the hydrological consequences of this process (Peel, 2009), despite important work on this question in South Africa and China (Turpie, Marais, & Blignaut, 2008;Yu et al, 2019).…”

Effects of Climate and Anthropogenic Drivers on Surface Water Area in the Southeastern United States

“…We found that anthropogenic drivers were more influential in estimating percent surface water area than climate drivers in our study region. Our findings are supported by similar studies identifying forested and urban land cover as the most important variables in estimating permanent surface water in the Northeast and Loess Plateau in China (Zeng et al., 2020), identifying increased water management from an expansion of agricultural area as the major source of lake volume decline in Urmia Lake in northwestern Iran (Chaudhari et al., 2018), and finding that drastic changes in vegetation cover changes the patterns of surface water in Canada (Egginton et al., 2014). Our finding that forest‐dominated land cover was the most important variable of all our climate and anthropogenic variables, supports other studies that found that surface water is significantly correlated with forested vegetation (Caldwell et al., 2016; Liu et al., 2021; Wei et al., 2017; Zeng et al., 2020).…”

Applications of forest hydrological science to watershed management in the 21st century.

“…We build on several recent discussions (e.g. National Research Council, 2008;Riveros-Iregui et al, 2011;Vose et al, 2012;Wang et al, 2012;Egginton et al, 2014) on the role of ecohydrology in addressing water resource challenges now and in the future. We focus our examples on forest watersheds in the southern US forests, as the complex mixture of public and private forest land ownership creates substantial challenges for watershed management at larger spatial scales.…”