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Precipitation and its relation to vegetation

Links between forests and water examined at the Global Landscapes Forum
Clouds rise over peat forest and oil palm plantations along the Belayan River in East Kalimantan, Indonesia. The relationship between trees, water and climate became the focus of recent discussions at the Global Landscapes Forum in Bonn, Germany. CIFOR Photo/Nanang Sujana

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Forests, trees and vegetation not only depend on rainfall but also play a critical role in generating it where they stand and in other locations, acting as a driving force for climate regulation.

This was the conclusion of a recent discussion forum hosted at the Global Landscapes Forum (GLF) in Bonn, Germany, where a diverse panel of speakers came together to discuss the concept of ‘rainfall recycling’.

A review article published earlier last year, titled Trees, forests and water: Cool insights for a hot world, showed that forest, water and energy interactions provide the foundations for carbon storage, cooling terrestrial surfaces and distributing water resources. Forests and trees must therefore be recognized as important regulators within water, energy and carbon cycles.

Following the release of the research paper, as well as a subsequent two-day virtual symposium on the topic, the GLF discussion on ‘Rainfall Recycling as a Landscape Function: Connecting SDGs 6, 13 and 15’ called for a paradigm shift – moving away from the current discourse about forests and climate change that focuses on sequestering and storing carbon.

The session instead put forward the role of forests and trees in the water cycle, showing new ways for forests and land management to influence the climate through atmospheric water cycle controls, and made connections to the Sustainable Development Goals (SDGs) – in particular, those on clean water and sanitation, climate action and sustaining life on land.

   A discussion on Rainfall Recycling as a Landscape Function: Connecting SDGs 6, 13 and 15 drew a crowd at the Global Landscapes Forum in Bonn, Germany. CIFOR Photo/Pilar Valbuena Perez


David Ellison, lead author of the research paper, gave the example of precipitation in the Blue Nile Basin originating from West African rainforests – an area which is seeing an increasing amount of deforestation.

“If deforestation continues on its current track, we could lose as much as 25 percent of the rainfall in the Ethiopian highlands,” he said.

“Forest-based ecosystems provide an ecosystem service that extends well beyond their ability to produce biomass – carbon sequestration – and this role must be nurtured,” he added, noting that the scale of the water cycle was also of importance.

Given that trees and forests are often seen as consuming water, through a process called evapotranspiration, Ellison questioned whether, when looking at the recycling effects, this should be called “consumption” or “production” of water resources.


As the discussion progressed, the panelists considered the implications of these insights on climate, land and water policies and actions.

CIFOR senior scientist Daniel Murdiyarso explained that recent data suggests deforestation is slowing and plantations are increasing, leading him to question what will happen with water.

“We need to find a new way of governing forests,” he said. “This has policy implications in terms of forests for water, or forests for climate, at the watershed level.”

“There are a lot of issues that are local, or national at the most,” Murdiyarso said, noting that carbon and climate agendas are often global.

Though this could be seen as a contradiction, the two sides can also complement one other: “In terms of the SDGs, this is […] globally relevant,” Murdiyarso explained, before adding that implementation on the ground is what matters.

   Water, trees and climate connected at a water reservoir in Brazil. CIFOR/Icaro Cooke Vieira


It was pointed out during the forum that much of the research being discussed had been known about for many years, and that bridging scientific knowledge and application was in fact the current and most pressing need.

The forum aimed to sketch a new agenda on water, land and climate to promote coordinated science-to-policy linkages, from cross-cutting policy integration to implementation on the ground, and to trigger interest for institutional and donor support for an otherwise sidelined topic.

A global scientific assessment looking at the interactions between forests and water, now being conducted by the Global Forests Expert Panel (GFEP) on Forests and Water, is expected to be presented by the middle of this year. This is set to inform the United Nations’ High-level Political Forum on Sustainable Development (HLPF), which is tasked with reviewing the implementation of the SDGs.

Vincent Gitz, Director of the CGIAR Research Program on Forests, Trees and Agroforestry (FTA), in closing the discussions in Bonn stated that “this is not new science per se, but it is science that is being refined.”

“Another question we can ask is, who can do what with this knowledge?” he said, referring to optimizing the contribution of forests and trees to the regulation of the water cycle. “We are waiting on the GFEP report to help us understand how the different institutions can embark on all of this science, and all the ramifications.”

Gitz added after the session that in light of the role of science and research to provide “early warnings” on preliminary findings – either because of new threats or new opportunities – the research could inform both policy and implementation.

It is expected that the findings and discussions will pave the way toward a more integrated approach to land, water and climate for the SDGs, and that moving forward, this body of research will continue to grow.

   FTA Director Vincent Gitz, far left, addresses the discussion panel at the Global Landscapes Forum. CIFOR Photo/Pilar Valbuena Perez
For more information on this topic, please contact Vincent Gitz at v.gitz@cgiar.org.
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