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Why Forests Matter for Water, Energy and Climate:
What we Think we Know
In Support of A WeForest Policy Brief
WeForest Steering Committee: David Ellison, Victoria Gutierrez, Cindy Morris, Bruno Locatelli,
Jane Cohen, Daniel Murdiyarso, Douglas Sheil
TheNileRiverBasin(workfromGebrehiwotetal.2015)
§ TheNileBasinprovidesthewaterresourcestofeedsome200millionpeople.
§ TheBlueNileBasinsuppliessome85%ofthetotalamountofwaterthatflowstothelowerNileRiver.
§ WhatisthesourceoftheBlueNilewaters?
FromaCatchmentBasin,WaterBalanceperspecJve(demand-sideapproach)
§ WewouldconsiderthetotalannualamountofprecipitaJonthatfallsintheBlueNileBasin
§ AndwewouldobservethatPrecipitaJonisparJcularlyheavyintheBlueNileBasinarea
§ Butshouldwegofurtherthanthis?
§ VisteandSorteberg(2013)suggestalargeshareoftheatmosphericmoisturethatfeedstheprecipitaJonintheBlueNileBasinoriginatesfromtheWestAfricanRainforests
§ ThereisanincreasingamountofdeforestaJoninthisarea
§ Someprojectasmuchasa25%reducJoninrainfallintheEthiopianHighlandswithconJnueddeforestaJon
(SolomonGebrehiwot,Gebrehiwotetal.2015)
ROC (Upwind)
ETL
OE
Precipita
3on
WES
ETREC ETOUT
WPROD
ETIN
Catchment Basin
RRL _________ (Share of
ETREC in P)
RRCON __________
(Share of ETIN in P)
WCONS
Defining the Concept of Hydrologic Space
R
To Downwind Locations
Precipita
3on
ET?
(Van der Ent et al., 2010)
(Bosilovich et al., 2002)
The Cross-Continental Transport of Atmospheric Moisture Matters
§ Land-atmosphereinterac1onsmaUerforthedistribuJonofwateracrossterrestrialandconJnentalsurfaces.
§ Onaverage,Forestsprovidemoreevapotranspira1on(atmosphericmoisture)forcross-conJnentaltransportthanotherlandcoversurfaces.
§ LandfurtherawayfromupwindcoastsistypicallyMOREdependentthanotherlands.
Con1nentalevapotranspira1onfeedsanimportantshareofterrestrial
Precipita1on
Atmospheric Moisture Transport Mechanisms
Virtuous cycle of increased Precipitation, ET and Forest Growth
(Layton and Ellison, under review)
How much Forest is enough?
(Biotic Pump, Makarieva et al.)
Icenuclea3onac3vemicroorganismsareimplicatedin«rainfallfeedback»
ICEPROPAGATION
COLONIZATION
ICENUCLEATION
TRANSPORTPRECIPITATION
DEPOSITION UPWARDFLUX
MULTIPLICATION MICROBIALSTOCK
(CindyMorris,Morrisetal.2014)
Forests as Rainfall and Bio-Precipitation Triggers
(Jan Pokorny, Hesslerova et al., 2013)
The Cooling Power of Forests
(Bounoua et al., 2015)
Urban Areas above/below 35%
Impervious Surface Area (ISA)
§ Forest-water interactions dissipate solar energy
§ Transpiration and Evaporation require and use energy
§ Surface cooling (lack of warming) is the result.
Canopy cover
What Drives Infiltration and Groundwater Recharge?
(Bargués Tobella et al.)
Gro
undw
ater
Rec
harg
e Transpiration Groundwater recharge
Dominant Paradigm
Transpiration Surface runoff Soil evaporation Groundwater recharge Infiltration G
roun
dwat
er R
echa
rge
Cloud Stripping / Fog Precipitation
Location( Elevation((m)( Annual(Rainfall((mm)(
Fog(Precipitation((mm)(
Fog(Precipitation((%(of(total(water(input)(
Panama% 500(1270% 1495(6763% 135(2299% 2.3(60.6%Puerto%Rico% 930(1015% 3204(4001% 0(436% 0(26.2%Costa%Rica% 1500% 3191% 886% 21.7%Colombia/Venezuela% 815(3100% 450(1125% 72(796% 3.5(48.3%
Guatemala% 2100% 2559% 23% <1%Guatemala% 2550% 2559% 203% 7.4%Hawaii% 981(3397% 300(2449% 134(832% 2.6(61.2%Mexico% 1330(2425% 215(1082% 0(339% 0(50.7%
Venezuela% 1750(2150% 828(1009% 354(592% 26(41.7%
% (Gazoul and Sheil, 2010) § What does this mean for the
Water Towers of the world? § How important are Cloud
Forests for the Water Balance? § What is the consequence of
deforestation?
The Importance of Spatial Organization
§ Where forests are located matters. § Land conversions impact land-atmosphere interactions and affect the
production of atmospheric moisture. § Up and downwind interactions may matter as much for the Water
Balance as up and downstream relationships. § Upwind sources of atmospheric moisture production affect both
Precipitation and the Water Balance and cannot be ignored. § Likewise, the catchment basin production of atmospheric moisture
matters for downwind locations.
Transboundary Relationships and Policy-Making
§ Because the supply of atmospheric moisture is transboundary in character, governance structures must consider these larger scale relationships.
§ Most water management frameworks, however, are focused on the local level, at much too small a scale.
§ And most climate policy frameworks are likewise structured either at the international or the national scale. These governance structures are again inadequate to the task.
§ Regional and continental scale governance structures are rare for catchment basin water management. And where they occur, they typically do not consider the supply (or re-export) of atmospheric moisture.
§ The international climate policy framework is focused on carbon. Should make positive relationships between forests, water, energy and climate primary.
Trees, Forests, Water, Energy and Climate How we Think they Matter
Forest cover plays an important role in the regional and continental hydrologic cycle.
More forest cover is, generally speaking, a good thing. It can raise precipitation and water availability in downwind locations. However, increasing forest cover in water poor areas can have negative consequences. (Natural balance matters).
In addition to down and upstream considerations, it is also important to think about down and upwind relationships. However, most assessments of the (local) Water Balance fail to do this.
Forests represent powerful adaptation tools: In the appropriate surroundings, forests can positively impact atmospheric moisture production, cooling, rainfall, infiltration, groundwater recharge, and other positive features (flood moderation, biodiversity, etc.).
Livelihoods depend upon our recognition of the transboundary nature of Hydrologic Space. Water and Energy cycles should be placed at the core of water and land use management and planning strategies. Carbon is secondary. Time for paradigm change. (Blue Nile Basin?)
