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251
ISSN 0041-6436
An international journal of forestry and forest industries Vol. 70 2019/1
FORESTS: NATURE-BASED
SOLUTIONS FOR WATER
Forest and Water Programme
The FAO Forest and Water Programme this vision by facilitating the sharing
envisions a world in which resilient of knowledge and experiences,
forest landscapes are managed developing the capacity of forest,
effectively to provide sustainable land and water managers to manage
water ecosystem services. In the forest–water nexus, and
collaboration with partners from the providing tools to support
forest and water sectors, it supports decision-making.
countries and stakeholders in realizing
More information:
www.fao.org/in-action/forest-and-
water-programme
Unasylva is published in English, French and Spanish. Subscriptions can be obtained by Cover: Aerial view of a village near Phang
sending an e-mail to unasylva@fao.org. Subscription requests from institutions (e.g. libraries, Nga Bay, Thailand. Forests and water have
companies, organizations and universities) rather than individuals are preferred in order to always been inextricably entwined.
make the journal accessible to more readers. All issues of Unasylva are available online free of © iStock.com/Oleh Slobodeniuk
charge at www.fao.org/forestry/unasylva.
Comments and queries are welcome at unasylva@fao.org
251ISSN 0041-6436
An international journal of forestry and forest industries Vol. 70 2019/1
Editor: A. Sarre
Editorial Advisory Board: N. Berrahmouni, J.
Campbell, P. Csoka, J. Fox, H. Abdel Hamied, D.
Contents
Hewitt, T. Hofer, H. Ortiz, L. Pina, E. Springgay,
A. Taber, S. Wertz, Xia, Z., E. Yazici, Zhang, D. Editorial 2
Emeritus Advisers: J. Ball, I.J. Bourke,
C. Palmberg-Lerche, L. Russo E. Springgay
Proofreader: Jana Gough Forests as nature-based solutions for water 3
Designer: Roberto Cenciarelli
D. Ellison, L. Wang-Erlandsson, R. van der Ent and M. van Noordwijk
The designations employed and the presentation of material Upwind forests: managing moisture recycling for
in this information product do not imply the expression of any
opinion whatsoever on the part of the Food and Agriculture nature-based resilience 14
Organization of the United Nations (FAO) concerning the legal
or development status of any country, territory, city or area or A.D. del Campo, M. González-Sanchis, U. Ilstedt, A. Bargués-Tobella
of its authorities, or concerning the delimitation of its frontiers
or boundaries. The mention of specific companies or products and S. Ferraz
of manufacturers, whether or not these have been patented,
does not imply that these have been endorsed or recommended
Dryland forests and agrosilvopastoral systems: water at the core 27
by FAO in preference to others of a similar nature that are not
mentioned. M. Gustafsson, I. Creed, J. Dalton, T. Gartner, N. Matthews, J. Reed,
The views expressed in this information product are those of L. Samuelson, E. Springgay and A. Tengberg
the author(s) and do not necessarily reflect the views or policies Gaps in science, policy and practice in the forest–water nexus 36
of FAO.
ISBN 978-92-5-131910-9 R. Lindsay, A. Ifo, L. Cole, L. Montanarella and M. Nuutinen
© FAO, 2019 Peatlands: the challenge of mapping the world’s invisible stores
of carbon and water 46
D.W. Hallema, A.M. Kinoshita, D.A. Martin, F.-N. Robinne, M. Galleguillos,
Some rights reserved. This work is made available under S.G. McNulty, G. Sun, K.K. Singh, R.S. Mordecai and P.F. Moore
the Creative Commons Attribution-NonCommercial-
ShareAlike 3.0 IGO licence (CC BY-NC-SA 3.0 IGO; https:// Fire, forests and city water supplies 58
creativecommons.org/licenses/by-nc-sa/3.0/igo/legalcode).
L. Spurrier, A. Van Breda, S. Martin, R. Bartlett and K. Newman
Under the terms of this licence, this work may be copied,
redistributed and adapted for non-commercial purposes, Nature-based solutions for water-related disasters 67
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FAO Forestry 75
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EDITORIAL
W
ater – clean, drinkable water – is likely to be one of relationship between forests and water) in policies and practice.
the most limiting resources in the future, given the Managing this nexus will be crucial for achieving many of the
growing global population, the high water demand Sustainable Development Goals, but it requires taking a landscape
of agricultural production systems and urban centres, and the approach. The ability to do this suffers from a lack of knowledge
confounding effects of climate change. We need to manage water about the factors that regulate the multiple functions of landscapes,
wisely – efficiently, cost-effectively and equitably – if we are to their interactions, and, ultimately, their effects on water users.
avoid the calamity of a lack of usable water. The authors describe opportunities to address the forest–water
Forested watersheds provide an estimated 75 percent of the nexus at the landscape scale, and they make recommendations
world’s accessible freshwater resources, on which more than half for research to help fill the gaps in knowledge.
the Earth’s people depend for domestic, agricultural, industrial Lindsay et al. make the case for much more policy attention on
and environmental purposes. Sustainable forest management is peatlands, which, they say, are often unrecognized or ignored and
essential, therefore, for good water management, and it can pro- therefore subject to widespread drainage and land-use conversion.
vide “nature-based solutions” for many water-related challenges. Yet peatlands contain huge stores of carbon and their destruction
This edition of Unasylva explores the challenges in realizing or mismanagement, therefore, could add substantially to global
the potential. warming. For example, even a shallow peat (30 cm deep) contains
In her article, Springgay explains that nature-based solutions more carbon than does primary tropical rainforest. Peatlands are
in water management involve the management of ecosystems also huge freshwater reservoirs and their loss could have major
(forested or otherwise) to mimic or optimize natural processes in implications for the sustainability of water supplies. Part of the
the provision and regulation of water. In many parts of the world problem in gaining more recognition for peatlands is that they
today, water management relies largely on “grey” infrastructure can be difficult to identify, and the authors provide a simple test;
involving the use of concrete and steel. A move towards nature- they also make recommendations for policymakers on how to
based solutions, says Springgay, requires a transformative shift in tackle this substantial but largely hidden challenge.
thinking in which forests and other ecosystems are viewed and Hallema and co-authors look at the implications of chang-
managed as freshwater regulators. She makes several recommen- ing forest fire regimes for forest and water management. The
dations to facilitate the transition towards “green” infrastructure increasing occurrence of extreme wildfires is threatening the
in water management. capacity of forests to deliver clean water. The authors say that
In their article, Ellison et al. present startling findings on the developing cost-effective strategies for managing fire and water
role of forests in multiplying the oceanic supply of freshwater in light of climate change, increasing urbanization and other
through moisture recycling (in which rainfall is returned to the trends requires a better understanding of the regional impacts and
atmosphere through evapotranspiration, making it available interactions of fire. Forests that are important for water supply
downwind to fall again as rain). Forests, say the authors, exhibit but at risk of extreme wildfire need to be identified and actively
more intense moisture recycling than non-forest land cover, managed, requiring the involvement of forest managers, hydrolo-
partly because of their larger water-storage potential, which, in gists, wildfire scientists, public-health specialists and the public.
turn, enables them to return rainfall to the atmosphere even in Finally, Spurrier et al. look at the crucial role of mangroves in
dry periods. Mapping the sources and sinks of precipitation and reducing the risk of disaster for millions of vulnerable coastal
evaporation can indicate where forest restoration efforts will people. Despite their importance, mangroves continue to decline
be most effective in maximizing moisture recycling for drier in extent, and climate change and other pressures threaten them
areas downwind. There is a desperate need, say the authors, to further. To help maintain the disaster-risk-reduction role of man-
redesign institutional frameworks to take into account long- groves and other natural (or green) infrastructure, the authors
distance forest–water relationships and their feedback effects recommend the use of adaptive frameworks and decision-support
on water availability. tools that enable managers to integrate and continuously update
Del Campo and co-authors present three case studies to show projections of climate-change risk, land use and human population
how “water-centred” management approaches can increase the growth.
resilience of dryland forests in the face of climate change. For Forests and water have always been inextricably entwined,
example, judicious management of Aleppo pine forest in a dry and forest managers have always needed to consider hydrology
region of Spain can increase tree growth and vigour and protect in their management decisions. But as resources become more
soils while adding to catchment water budgets and downstream constrained and water demand grows ever greater, water manage-
water flows. Such “ecohydrological-based forest management” ment will inevitably come even more to the fore in forest-related
can increase water availability in water-limited environments decision-making. Recognizing the importance of the forest–water
and therefore also socio-ecological resilience. nexus is the first step in building it into institutional processes
Gustaffson and co-authors look at gaps in the knowledge and finding forest-based solutions for water.
required to fully incorporate the forest–water nexus (i.e. the
3
© FAO/DANIEL HAYDUK
Forests as nature-based solutions for water
E. Springgay
G
A transformation is needed from rowing populations and increasing approaches to water management are
conventional forest management industrialization, urban develop- inadequate for ensuring the well-being
approaches to nature-based ment and demand for food and of human populations, biodiversity and
solutions that make water-related consumer goods have led to large-scale ecosystems.
ecosystem services the primary land-cover and land-use change globally, An estimated 65 percent of water fall-
objective. which has, in turn, caused hydrological ing on land is either stored within soil or
changes. It is also increasingly apparent evaporated from soil and plants (Oki and
that much of the human-made grey-water Kanae, 2006), with 95 percent of the soil
infrastructure,1 such as dams, pipes, ditches water stored within or above groundwater
and pumps, has contributed to global zones (Bockheim and Gennadiyev, 2010).
problems and that business-as-usual Therefore, terrestrial ecosystems are
important for land–water–energy balances,
influencing soil water and atmospheric
1
Grey infrastructure generally refers to engi-
neering projects that use concrete and steel, moisture availability and thus affecting
green infrastructure depends on plants and eco
systems, and blue infrastructure combines green
Elaine Springgay is Forestry Officer at the FAO spaces with good water management (Sonneveld Above: Forests as a nature-based solution
Forestry Department, Rome, Italy. et al., 2018). for water, United Republic of Tanzania
Unasylva 251, Vol. 70, 2019/1
4
climate (Huntington, 2006; Ellison et al., to achieve the social, economic and water for human consumption, industry
2017; Creed and van Noordwijk, 2018). All environmental goals embedded in these; and the environment.
forests influence water (FAO, 2018b), from it is essential, therefore, to strategically Land-use decisions can have significant
cloud forests and tree-covered wetlands integrate natural solutions, including consequences for water resources, com-
upstream to dryland and coastal forests green and blue infrastructure, into overall munities, economies and environments
downstream. It has been estimated that management approaches. The integration in distant (downstream and downwind)
forested watersheds provide 75 percent of of nature-based solutions shows promise locations. The loss of natural forests may
the world’s accessible freshwater resources for addressing water scarcity through increase water yields in the short term
and that more than half the Earth’s popula- supply-side management, particularly by but have long-term negative impacts on
tion is dependent on these water resources increasing water quality and groundwater water quantity and quality. For example,
for domestic, agricultural, industrial and recharge, which ultimately is essential for evapotranspiration from the Amazon River
environmental purposes (Millennium sustainable food production, improved and Congo River basins is a major source
Ecosystem Assessment, 2005). Forests are human settlements, access to water supply of precipitation (around 50–70 percent)
sometimes referred to as natural infrastruc- and sanitation, water-related risk reduc- in the Rio de la Plata basin and the Sahel,
ture, and their management can provide tion, and building resilience to climate respectively (Van der Ent et al., 2010;
“nature-based solutions” for a range of variability and change (UNWWDR, 2018). Ellison et al., 2017). Large-scale forest
water-related societal challenges. This It is estimated that USD 10 trillion will loss and land conversion affect these
article explores that potential. need to be invested in grey infrastructure natural processes, reducing cloud cover
between 2013 and 2030 for adequate and precipitation downwind (Ellison et
FORESTS: NATURAL water management (Dobbs et al., 2013). al., 2017; Creed and van Noordwijk, 2018).
INFRASTRUCTURE FOR WATER Nature-based solutions could reduce this Forest restoration and tree planting will
Nature-based solutions are actions that investment burden while also improving likely improve water quality, with the
protect, sustainably manage and restore economic, social and environmental out- impacts of such interventions depend-
natural and modified ecosystems in ways comes. Nearly USD 24 billion is estimated ing on species, management regime and
that effectively and adaptively address to have been spent on green infrastructure temporal and spatial scale. It is estimated
societal challenges and deliver benefits for water in 2015, benefiting 487 million that land conservation and restoration,
for human well-being and biodiversity hectares of land (Bennet and Ruef, 2016). including forest protection, reforestation
(Cohen-Shacham et al., 2016). In water Paying greater attention to landscape man- and agroforestry, could lead to a reduc-
management, nature-based solutions agement, including integrated watershed tion of 10 percent or more in sediments
involve the management of ecosystems management, land protection, reforestation and nutrients in watersheds (Abell et al.,
to mimic or optimize natural processes, and riparian restoration, could reduce the 2017). Care is needed, however, to ensure
such as vegetation, soils, wetlands, water operational and maintenance costs of that achieving water-quality goals does
bodies and even groundwater aquifers, grey infrastructure (Echavarria et al., not result in unacceptable trade-offs with
for the provision and regulation of water. 2015; Box 1). water yield.
The adoption of nature-based solutions In addition to their water-related eco
for water requires a transformative shift in The role of forests in hydrology system services, forests provide habitat for
thinking from demand- to supply-oriented All forests affect hydrology and so, there- fish and other aquatic species, which, in
water management and planning, in which fore, does their management. Forests turn, play roles in ensuring the function-
crucial ecosystems such as forests are seen and trees use water and provide many ality of these ecosystems. The quantity,
not only as users but also as regulators of provisioning, regulating, supporting and quality, temperature and connectivity of
fresh water. cultural ecosystem services. Forested water resources influence fish populations
Nature-based solutions have gained areas and landscapes with trees, there- and aquatic biodiversity. Changes in these
attention in recent years because of their fore, are integral components of the water factors can affect species richness, even-
potential for addressing water scarcity cycle, regulating streamflow, fostering ness and endemism, thus influencing the
and contributing to the achievement of the groundwater recharge and contributing biodiversity and food systems of dependent
Sustainable Development Goals (SDGs), to atmospheric water recycling, including populations.
the Paris Agreement on climate change, cloud generation and precipitation through Many fish and other aquatic organisms
the Sendai Framework for Disaster Risk evapotranspiration. Forested areas and are sensitive to ecosystem degradation,
Reduction, the Aichi Biodiversity Targets, landscapes with trees also act as natural such as through eutrophication, habitat
and other international commitments. Grey filters, reducing soil erosion and water degradation and fragmentation, acidifi-
infrastructure alone will be insufficient sedimentation, thus providing high-quality cation, and changes in temperature and
Unasylva 251, Vol. 70, 2019/1
5
Box 1
Forest management: nature-based solution for urban water supply
Ninety percent of major cities rely on forested watersheds for their water supply (McDonald and Shemie, 2014), with one-third of the world’s
largest cities, including Bogotá, Johannesburg, New York, Tokyo and Vienna, obtaining a large proportion of their drinking water from pro-
tected forest areas (Dudley and Stolton, 2003).
Source-water protection, including through forest restoration and trees on agricultural land, could improve water quality for more than 1.7
billion people living in cities at a cost of less than USD 2 per person per year (which would be offset by savings from reduced water treatment)
(World Bank, 2012; Abell et al., 2017). For example, a forest-based initiative to reduce water pollution from agriculture has saved the City
of New York from the need to install a treatment plant (at an estimated cost of USD 8 billion–10 billion), as well as an additional USD 300
million per year in operational and maintenance costs. New York City has the largest unfiltered water supply in the United States of America
(Abell et al., 2017). Similarly, the estimated water conservation value of Beijing’s forests is USD 632 million (approximately USD 689 per
ha) per year (Biao et al., 2010).
Forests are used as nature-based solutions for water-related natural hazards. In Peru’s Pacific Coast water basin, where an estimated two-thirds
of historical tree cover has been lost (WRI, 2017), integrating green and grey infrastructure could reduce Lima’s dry-season deficit by 90
percent, and this would be more cost-effective than implementing grey infrastructure alone (Gammie and de Bievre, 2015). Likewise, local
forest restoration is being used in Malaga, Spain, to mitigate flood risk.
As urban populations grow, ecosystems and their services will increasingly be pushed to their limits (Kalantari et al., 2018). This is particularly
true in the fastest-growing cities – small and medium-sized cities that are undergoing rapid and mostly unplanned expansions of their urban
areas but which may need to rely increasingly on watersheds for water supply. Of the three fastest-growing cities in Africa and Asia (based
on United Nations data), an unpublished FAO review has determined that only Kampala, Uganda, acknowledges the water-related services
provided by forests.
The potential of forest management to provide nature-based solutions to mitigate some of the challenges of urban development needs to be
considered in spatial planning and management strategies (Kalantari et al., 2018). To grow sustainably, cities will need to play active roles in
protecting the water sources on which they depend.
Children cross
a river in the
Philippines. It
is important to
manage forests
© FAO/JAKE SALVADOR
and trees with
water ecosystem
services in mind
and to maximize
the forest benefits
for water
Unasylva 251, Vol. 70, 2019/1
6
climate (FAO, 2018a). For example, the six in the past 100 years, in direct cor- health and well-being, the environment
number of threatened and endangered relation with population growth (Wada et and sustainable development (Veolia and
freshwater species has increased due to the al., 2016); water consumption continues IFPRI, 2015). For example, an estimated
poor health of inland water systems (FAO, to grow at about 1 percent per year (FAO, 80 percent of all industrial and municipal
2018a). The Living Planet Index indicates undated). The global population is pro- wastewater is released into the environment
an 83 percent decline in freshwater species jected to increase from 7.7 billion in 2017 to without treatment (WWAP, 2017). Changes
populations since 1970 (WWF, 2018). 9.4 billion–10.2 billion people in 2050, with in water sediment loads and temperature
Forests and trees can help mitigate minor two-thirds living in cities (United Nations, can significantly affect fish populations
to moderate flooding events, control ava- 2018). Global water demand is projected and aquatic biodiversity, which may fur-
lanches, combat desertification, and abate to rise by 20–30 percent by 2050, due to ther affect dependent food chains and food
storm surges. For example, mangrove for- population growth, associated economic security (FAO, 2018a).
ests act as protective shields against wind development, changing consumption pat- Changes in land cover and use, population
and wave erosion, storm surges and other terns, land-use change and climate change, growth, and the frequency and intensity of
coastal hazards (FAO, 2007; Nagabhatla, among other factors (Burek et al., 2016; extreme events associated with a changing
Springgay and Dudley, 2018), and trees in WWAP, 2018). climate increase the risk of water-related
drylands help abate soil erosion and drought Under a business-as-usual scenario, the disasters. Since 1992, floods, droughts and
by capturing fog water, reducing surface world is projected to face a 40 percent water storms have affected 4.2 billion people and
water runoff and promoting groundwater deficit by 2050 (WWAP, 2015). Domestic caused USD 1.3 trillion in damage world-
recharge (Ellison et al., 2017). Changes in water use will increase significantly in wide (UNESCAP/UNISDR, 2012). Floods
land use – such as large-scale deforesta- all regions, particularly Africa and Asia, have become more frequent, increasing
tion or, conversely, forest restoration – can where domestic demand is expected to from an average of 127 events per year
influence the resilience of landscapes in triple, and in Central and South America, in 1995–2004 to 171 events per year in
the face of water-related natural hazards. where estimated future demand is double 2005–2014; floods have accounted for 47
It is important, therefore, to manage current withdrawals (Burek et al., 2016). At percent of all weather-related disasters
forests and trees with water ecosystem the same time, food demand is expected to since 1995 and affected 2.3 billion people
services in mind and to maximize the forest increase by 60 percent, requiring more land (CRED and UNISDR, 2015).
benefits for water and mitigate negative for food production and causing impacts It is estimated that floods, droughts and
impacts. A range of management deci- on soil and water resources that likely will storms result in average global losses
sions, such as species selection, stocking lead to further degradation (FAO, 2011b). of USD 86 billion per year across all
densities, and location in the landscape, Meanwhile, less than 1 percent of the economic sectors, with Africa and Asia
can have important effects on hydrology. total available freshwater is allocated for most affected in terms of deaths, dam-
Managing forests for multiple benefits is maintaining the health of ecosystems that aged communities and economic losses.
the foundation of sustainable forest man- serve as natural infrastructure for water The cost of floods, droughts and storms
agement, but it requires an understanding (Boberg, 2005; Nagabhatla, Springgay and worldwide is expected to escalate to USD
and recognition of trade-offs. For example, Dudley, 2018). 200 billion–400 billion per year by 2030
fast-growing exotic species planted for bio- Approximately 80 percent of the world’s (OECD, 2015).
mass and carbon sequestration may have a population suffers from moderate to severe The impacts of disasters could be miti-
positive impact on water quality but could water scarcity (Mekonnen and Hoekstra, gated if land and forest conversion, urban
greatly reduce water supply. Reducing tree 2016). Nearly half the global population is expansion and planning, and the intensifica-
densities, prolonging rotation cycles and already living in areas with potential water tion of food production take ecological
conserving native forests in riparian buffer scarcity at least one month per year, and it functions into account and aim to improve
zones could mitigate these negative effects. is estimated that this will increase to 4.8 – rather than degrade – ecosystem services.
billion–5.7 billion people – more than half 2
According to the Ramsar Convention on Wet-
WATER: A GLOBAL CHALLENGE the projected global population – by 2050 lands (2016), wetlands “are areas of marsh, fen,
Davidson (2014) estimated that up to 87 (Burek et al., 2016). peatland or water, whether natural or artificial,
percent of all wetlands, 2 including tree- Water pollution has worsened in almost permanent or temporary, with water that is static
or flowing, fresh, brackish or salt, including areas
covered wetlands and peatlands, have been all rivers in Africa, Asia and Latin of marine water the depth of which at low tide
lost worldwide since the eighteenth cen- America since the 1990s (UNEP, 2016; does not exceed six metres”. They “may also
tury; up to 71 percent of all wetlands have WWAP, 2018), and the degradation of incorporate riparian and coastal zones adjacent
to the wetlands, and islands or bodies of marine
been destroyed since 1900. Global water water resources is expected to increase water deeper than six metres at low tide lying
consumption has increased by a factor of in the next decades, threatening human within the wetlands”.
Unasylva 251, Vol. 70, 2019/1
7
© FAO/JOAN MANUAL BALIELLAS
A forest park in Hanoi,
Viet Nam. Forests and
water go arm-in-arm
Box 2
Incentivizing forest–water management
Payment for ecosystem services (PES) schemes constitute a potential incentive mechanism for better environmental management. Applied to
forest–water management, PES schemes require service “buyers” (usually downstream communities and industries) and service “providers”
(upstream communities who are considered forest stewards). PES schemes have limitations, however: for example, they rely on the complex
valuation of ecosystem services, often require formal land-tenure arrangements, depend on evidence that services are delivered, and can have
implications for socio-economic power dynamics. These limitations may explain the lack of successful PES schemes.
Other incentive mechanisms exist. For example, “reciprocal watershed agreements” are simple grassroots versions of conditional transfers
that help land managers in upper watershed areas to sustainably manage their forest and water resources in ways that benefit both themselves
and downstream water users. Like PES, reciprocal watershed agreements depend on an understanding that hydrological services are being
provided, and they rely on recognized conditions of tenure at the local level (i.e. who owns, controls and grants access to watershed forests).
In contrast to PES schemes, however, reciprocal watershed agreements offer demand-led rewards rather than monetary incentives, with
compensation based on specific needs that diversify income sources. For example, downstream water users could provide upstream landowners
with improved livelihood options such as beehives, fruit-tree seedlings and better irrigation equipment (Porras and Asquith, 2018).
Reciprocal watershed agreements have been implemented successfully in Bolivia (Plurinational State of), where more than 270 000 water users
have signed agreements with 6 871 upstream landowners to conserve 367 148 ha of water-producing forests. In return, the reciprocity-based
conservation agreements provide sufficient funding for alternative development projects such as drip irrigation, fruit and honey production and
improved cattle management. Fifty-two municipalities in the country have adopted such agreements since 2003 (Natura Foundation, 2019).
The success of reciprocal watershed agreements in Bolivia (Plurinational State of) may be due partly to the fact that the agreements have
been made in areas with cloud forests: people can see that deforestation reduces dry-season flows and that improved cattle management that
restricts livestock movement improves water quality. In such cases, upstream conservation measures can easily be shown to contribute to the
protection of watershed services – without the need for detailed and costly hydrological assessments.
In addition, scale and local perceptions of forest–water links matter. The watersheds subject to the agreements are small, and there is a limited
number of land uses and stakeholders; it is easier, therefore, to see the benefits of improved management, and land managers and water users
can easily be identified. Moreover, the mechanism is likely to be more successful in areas where local stakeholders already understand and
perceive the links between forest management and maintaining healthy freshwater ecosystems.
Unasylva 251, Vol. 70, 2019/1
8
A GLOBAL PICTURE OF FORESTS Despite growing recognition of the for example, the United States Forest
AND WATER influence and importance of forests for Service identifies itself as the manager of
An estimated 31 percent of the global land water, only 25 percent of forests globally the nation’s largest water resource (United
area is forested, of which 65 percent is are managed with soil and water conser- States Forest Service, 2017). Europe falls
degraded (FAO, 2010; 2015). The World vation as one of the primary objectives below the global average of managing
Resources Institute calculates tree-cover (Figure 1). Moreover, a little less than 10 forests for soil and water conservation
trends by major water basin, 3 or hydro- percent of forests is managed primarily because most forest land is privately owned
shed, as well as water-related hazard risk for soil and water conservation, includ- and is not accounted for in national report-
(i.e. erosion, forest fire and baseline water ing around 2 percent managed primarily ing; however, a recent report provided
stress4). Before 2000, hydrosheds averaged for clean water and about 1 percent each ample evidence of integrated approaches to
68 percent tree cover; this had reduced to for coastal stabilization and soil erosion forest–water management in Europe (FAO
31 percent by 2000, however, and to 29 control (FAO, 2015). Only 13 countries and UNECE, 2018). In many countries in
percent by 2015. This tree-cover loss has report that all their forests are managed the tropics and subtropics, however, there
not necessarily been evenly distributed: with consideration given to soil and water
approximately 38 percent of the hydro- conservation. 3
FAO divides the world into 230 major basins or
sheds had lost more than half their tree More than 70 percent of forests in North watersheds (FAO, 2011a).
cover by 2000, rising to 40 percent by 2014 America are managed with consider- 4
Baseline water stress is defined as the ratio of
total water withdrawals to total renewable water
(WRI, 2017). ations for soil and water conservation; supply in a given area (WRI, 2017).
1
Percentage area of
forests for soil and
water conservation
by country and
forest type
0
90
no data
1990 2000 2005 2010 2015
500 000
HECTARES
400 000
300 000
200 000
100 000
0
BOREAL TEMPERATE SUBTROPICAL TROPICAL
Source: FAO (2018b).
Unasylva 251, Vol. 70, 2019/19
is a negative trend in the area of forests as floods, forest fires, landslides and storm Sustainable Development Goals
managed for soil and water conservation, surges. Of the hydrosheds that had lost The interconnection between forests and
and deforestation is also ongoing. Although at least half their tree cover by 2015, 88 water is explicitly referenced in two SDGs:
all forests have impacts on hydrology, the percent had a medium to very high risk of SDG 6 (“Clean water and sanitation”) and
loss of tropical and subtropical forests erosion, 68 percent had a medium to very SDG 15 (“Life on land”). In SDG target
may disproportionately affect the global high risk of forest fire, and 48 percent had a 6.6, forests are recognized as water-related
hydrological cycle (FAO, 2018b). medium to very high risk of baseline water ecosystems; similarly, SDG target 15.1
Decreases in tree cover can lead to stress (WRI, 2017) (Figure 2). refers to forests as freshwater ecosystems.
increased soil erosion and degradation Although the indicators for these targets
and, in turn, to a reduction in water qual- BUILDING ON INTERNATIONAL do not measure the interlinkages between
ity. In some cases, the loss of tree cover MOMENTUM forests and water, methodologies exist
is also associated with reduced water The notion of forest management as a for looking at this relationship – which
availability, especially when natural for- nature-based solution for water is not new. countries could use to better understand
ests are converted to other land uses that The forest–water relationship is a cross- and report on how forests serve as natu-
degrade or compact soils, thus reducing cutting issue, and it has gained increased ral infrastructure for water. For example,
soil infiltration, water storage capacity and attention in the last two decades (Figure 3). in addition to the indicator used in the
groundwater recharge (Bruijnzeel, 2014; The UN Decade on Ecosystem Restoration FAO Global Forest Resources Assessment
Ellison et al., 2017; FAO, 2018b). The forest (2021–2030) will undoubtedly raise the (“area of forests managed for soil and water
loss and degradation associated with land profile of forest management as a nature- conservation”), Ramsar (2019) specifies
conversion and poor land management based solution for water to new heights other forested or tree-covered areas, such
practices may also increase the risk to and because of the wide-ranging potential as peatlands, as wetlands. Around 123
damage from water-related hazards, such impacts of restoration on hydrology and million ha of forest – about 2.9 percent of
the need to take these into account in plan- the world’s forest area – are classified as
2 ning restoration initiatives. Ramsar sites.
Hydroshed risk to erosion and base water
stress, by percentage tree cover loss
Erosion risk by % tree cover loss Baseline water stress risk Forest fire risk by
by % tree cover loss (2015) % tree cover loss (2015)
35 35 35
30 30 30
Very high Very high Very high
High High High
Medium 25 Medium 25 Medium 25
Low Low Low
Very low Very low Very low
20 20 20
15 15 15
10 10 10
5 5 5
0 0 0
90% 80% 70% 60% 50% 40% 30% 20% 10% 90% 80% 70% 60% 50% 40% 30% 20% 10%
90% 80% 70% 60% 50% 40% 30% 20% 10%
Source: WRI (2017).
Unasylva 251, Vol. 70, 2019/110
3
Recent global forest policy initiatives that could encourage nature-based solutions for water
Sustainable Development Goals
• SDG 6: Clean water and sanitation
• SDG 13: Climate action
• SDG 14: Life below water
• SDG 15: Life on land
• Other SDGs also apply, including SDG 1 (No poverty); SDG 2 (Zero hunger); SDG 8 (Decent work and economic
growth); and SDG 11 (Sustainable cities and communities)
United Nations Convention to Combat Desertification
• Strategic Objective 1: To improve the condition of affected ecosystems, combat desertification/land degradation,
promote sustainable land management and contribute to land degradation neutrality
• Strategic Objective 2: To improve the living conditions of affected populations
• Strategic Objective 3: To mitigate, adapt to and manage the effects of drought in order to enhance the resilience
of vulnerable populations and ecosystems
• Strategic Objective 4: To generate global environmental benefits through effective implementation of the Convention
Convention on Biological Diversity Aichi Targets
• Target 1: People are aware of the values of biodiversity and the steps they can take to conserve and use it sustainably
• Target 4: Sustainable production and consumption with impacts of use of natural resources well within safe
ecological limits
• Target 5: Rate of loss of all natural habitats, including forests, is at least halved and where feasible brought close
to zero, and degradation and fragmentation is significantly reduced
• Target 7: Areas under agriculture, aquaculture and forestry are managed sustainably, ensuring conservation of
biodiversity
• Target 11: Terrestrial and inland water, and coastal and marine areas of particular importance for biodiversity and
ecosystem services, are conserved
• Target 14: Ecosystems that provide essential services, including services related to water, and contribute to health,
livelihoods and well-being, are restored and safeguarded
• Target 15: Ecosystem resilience and the contribution of biodiversity to carbon stocks has been enhanced through
conservation and restoration
Other international processes
• United Nations Framework Convention on Climate Change – countries have made commitments under the Paris
Agreement through their nationally determined contributions and national adaptation plans
• Sendai Framework for Disaster Risk Reduction: Priority 1 – Understanding disaster risk; Priority 2 – Strengthen-
ing disaster risk governance to manage disaster risk; Priority 4 – Enhancing disaster preparedness for effective
response and to “build back better” in recovery, rehabilitation and reconstruction
• Ramsar Convention on Wetlands: Strategic Goal 1 – Addressing the drivers of wetland loss and degradation;
Strategic Goal 3 – Wisely using all wetlands
• Forest landscape restoration – countries have made commitments on land restoration by 2030, many including
water-related objectives
Unasylva 251, Vol. 70, 2019/111
(Intended) nationally determined To do this, a scientific understanding of the and building social and environmental
contributions context is needed, including the well-being resilience (FAO and UNECE, 2018).
Forests and water resources feature and needs of communities and ecosystems. A key challenge of management is to
prominently in the nationally determined A transformation in approach may be optimize the multiple benefits and mini-
contributions of countries to the Paris required for a rapid transition from tradi- mize the trade-offs.
Agreement on climate change. Eighty- tional forest management options, such as • Increase connectivity within
eight percent of the original “intended” silviculture for wood production or conser- and between landscapes. Hydrol-
nationally determined contributions of vation, to regimes in which the provision of ogy connects landscapes, including
countries referenced forests as part of land water-related ecosystem services is the pri- upstream and downstream water bod-
use, land-use change and forestry, and 77 mary objective. Nature-based solutions do ies and related terrestrial ecosystems;
percent referenced water (French Water not necessarily require additional financial atmospheric water teleconnects land-
Partnership and Coalition Eau, 2016). resources; rather, they have the potential to scapes at the continental scale. The
Forty-nine percent of 168 (intended) enable the more effective use of existing conservation and restoration of upland
nationally determined contributions refer financing (WWAP, 2018) by increasing the forests and peatlands, the establishment
to the interlinkages between forest and value of multiple forest goods and services, of riparian networks, and the restora-
water management, including references including water, and reducing investments tion of meandering water courses and
to integrated (water) resource manage- in grey infrastructure. wetlands will help maintain the hydro-
ment and the water ecosystem services The following recommendations are logical functionality of landscapes, and
provided by forests and mangroves, with made to facilitate the rapid transition restored areas will also function as bio-
the majority of these references included towards nature-based solutions for water. diversity corridors for terrestrial and
under adaptation measures. Of the coun- • Implement science-based manage- aquatic species.
tries indicating their nationally determined ment and guidelines. Forest man- • Greatly intensify collaboration
contributions, those in Africa, Asia and agement for water ecosystem services among sectors. The integration
Latin America give most recognition to not only needs to take into account of nat u r a l a nd hu m a n-m a d e
the importance of forest management as a current environmental and socio- infrastructure is needed to address
nature-based solution for water (Springgay economic conditions but also future global water, land and urban
et al., forthcoming). projections related to land-use planning challenges effectively. This requires
Although nationally determined and climate scenarios. The aim of spe- forestry to collaborate with other
contributions do not imply resource cies selection, spacing, thinning and sectors, including water, agriculture,
commitments until 2020, the strong rotation cycles should be to optimize urban planning, disaster risk man-
acknowledgement of forest–water rela- water ecosystem services, biomass and agement and energy. Collaboration
tionships within them suggests there carbon storage and manage potential between ministries in governments
is significant political will to address trade-offs. Examples exist of landscape poses well-known challenges; at the
the issue, offering an opportunity to management (such as ecosystem-based local level, on the other hand, many
promote the integration of forests as management) that prioritizes ecosystem stakeholders – governments, landown-
nat u r a l i n f r a st r uct u r e i n wat er integrity and functionality, and these ers and businesses – are involved in
management. could be more widely employed and multiple sectors as managers of lands
integrated. and forests and their associated water
GLOBAL CHALLENGES NEED • Bundle benefits in schemes to better resources. Is it possible to engage with
CROSS-CUTTING, INTEGRATED compensate landowners and man- other sectors without fighting for juris-
SOLUTIONS agers for their water management dictional control? The forest sector
Changing the landscape changes the practices. Managing forests for water should consider marketing its skills
hydrology. This is true for all scenarios – can produce a wide range of other in forest management and long-term
whether tree-cover loss results in land-use goods and services, including carbon planning to other sectors reliant on
change, or a degraded landscape is restored sequestration, biodiversity conserva- sustainable forest and tree manage-
through reforestation or afforestation. To tion, cultural services (e.g. education ment as a nature-based solution for
fully take into account the impacts of and recreation), and wood and non- the immense challenges facing our
forest-related landscape change on water wood forest products. The bundling water resources. u
in land management decisions, it is neces- of the multiple benefits of forests is
sary to consider temporal and spatial scales a cost-effective means for increasing
as well as short- and long-term objectives. income opportunities for communities
Unasylva 251, Vol. 70, 2019/112
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Upwind forests: managing moisture recycling for
nature-based resilience
D. Ellison, L. Wang-Erlandsson, R. van der Ent and M. van Noordwijk
E
Trees and forests multiply the fficient and effective forest and however, tends to focus on river flows and
oceanic supply of freshwater water-related nature-based solu- to take rainfall for granted as an unruly,
through moisture recycling, tions to challenges in human devel- unmanageable input to the system (Ellison,
pointing to an urgent need to halt opment require a holistic understanding Futter and Bishop, 2012). Thus, the poten-
deforestation and offering a way to of the role of forest–water interactions tial impact of increased tree and forest
increase the water-related benefits in hydrologic flows and water supply in cover on downwind rainfall and potential
of forest restoration. local, regional and continental landscapes. water supply is both underestimated and
Forest and water resource management, underappreciated.
Afternoon clouds over the Amazon rainforest
© NASA IMAGE COURTESY JEFF SCHMALTZ, MODIS RAPID RESPONSE AT NASA GSFC
David Ellison is at the Department of Forest
Resource Management, Swedish University of
Agricultural Sciences, Umeå, Sweden, Adjunct
Researcher, Sustainable Land Management
Unit, Institute of Geography, University of Bern,
Switzerland, and at Ellison Consulting, Baar,
Switzerland.
Lan Wang-Erlandsson is at the Stockholm
Resilience Centre, Stockholm University,
Stockholm, Sweden.
Ruud van der Ent is at the Department of Water
Management, Faculty of Civil Engineering and
Geosciences, Delft University of Technology,
Delft, the Netherlands, and the Department of
Physical Geography, Faculty of Geosciences,
Utrecht University, Utrecht, the Netherlands.
Meine van Noordwijk is at the World
Agroforestry Centre, Bogor, Indonesia, and Plant
Production Systems, Wageningen University,
Wageningen, the Netherlands.
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