Presentation by David Ellison of the WeForest Steering Committee at the World Agroforestry COP21 side event on ecological rainfall infrastructure

1. 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

2. The Nile River Basin
(work from Gebrehiwot et al. 2015)
§ The Nile Basin provides the water resources
to feed some 200 million people.
§ The Blue Nile Basin supplies some 85% of the
total amount of water that flows to the lower
Nile River.
§ What is the source of the Blue Nile waters?
From a Catchment Basin, Water Balance
perspecJve (demand-side approach)
§ We would consider the total annual
amount of precipitaJon that falls in the
Blue Nile Basin
§ And we would observe that
PrecipitaJon is parJcularly heavy in the
Blue Nile Basin area
§ But should we go further than this?
§ Viste and Sorteberg (2013) suggest a large
share of the atmospheric moisture that feeds
the precipitaJon in the Blue Nile Basin
originates from the West African Rainforests
§ There is an increasing amount of deforestaJon
in this area
§ Some project as much as a 25% reducJon in
rainfall in the Ethiopian Highlands with
conJnued deforestaJon
(Solomon Gebrehiwot, Gebrehiwot et al. 2015)

3. ROC
(Upwind)
ETL
OE
Precipita3on
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
Precipita3on
ET?

4. (Van der Ent et al., 2010)
(Bosilovich et al., 2002)
The Cross-Continental Transport of Atmospheric Moisture Matters
§ Land-atmosphere interac1ons maUer for the
distribuJon of water across terrestrial and
conJnental surfaces.
§ On average, Forests provide more
evapotranspira1on (atmospheric moisture) for
cross-conJnental transport than other land
cover surfaces.
§ Land further away from upwind coasts is
typically MORE dependent than other lands.
Con1nental
evapotranspira1on
feeds an important
share of terrestrial
Precipita1on

5. 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.)

6. Ice nuclea3on ac3ve microorganisms are implicated in «rainfall feedback»
ICE PROPAGATION
COLONIZATION
ICE NUCLEATION
TRANSPORT
PRECIPITATION
DEPOSITION UPWARD FLUX
MULTIPLICATION MICROBIAL STOCK
(Cindy Morris, Morris et al. 2014)
Forests as Rainfall and Bio-Precipitation Triggers

7. (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.

8. Canopy cover
What Drives Infiltration and Groundwater Recharge?
(Bargués Tobella et al.)
GroundwaterRecharge
TranspirationGroundwater recharge
Dominant Paradigm
Transpiration Surface runoff Soil evaporation Groundwater rechargeInfiltrationGroundwaterRecharge

9. 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?

10. 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.

11. 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.

12. 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?)

13. Thanks for Listening!
Comments Welcome
(EllisonDL@Gmail.com)