Forests

Note: As mentioned in the Release notes, we have a small staff, and therefore have had to postpone some important material for the next release, scheduled for January 2018.  This is particularly true of forests and we will include a more thorough examination of their importance in addressing climate moving forward.  Nonetheless, we felt that the investigations here were innovative and interesting, and we wanted to make them available to our readers sooner rather than later.

Forests cover nearly 31% of Earth’s total land area [FAO 2016], and remain one of the major terrestrial ecosystems on the planet. Forests play a significant role in the global ecosystem through cooling, evapotranspiration, covering/shading/sheltering, providing fuel and fiber, aiding cloud formation, and creating wind. Because global forests and wooded lands store an estimated 485 Gt of carbon, forest conservation and afforestation are recognized in the United Nations Framework Convention on Climate Change (UNFCCC) as key strategies for climate change mitigation [UNFCCC 2017].  

Despite this acknowledgment, “for the world as a whole, carbon stocks in forest biomass decreased by an estimated 0.22 Gt annually during the period 2011–2015. This was mainly because of a reduction in the global forest area”  [UNFCCC 2017]. Indeed, humanity has been in the business of clearing forests for thousands of years, and this continues today. However, rapid reductions in deforestation could abate further carbon emissions and thus extreme results of climate change. Moreover, reductions in deforestation and implementation of agroforestry practices together could restore biodiversity in damaged ecosystems, repair local and global water cycles, and, ultimately, help restore carbon levels to pre-industrial levels. Here we present several articles illustrating the impact of forests on global climate, as well as the potential for restorative afforestation and agroforestry practices to sequester large amounts of carbon.

Forest Article Summaries

Ellison 2017.  This paper takes the innovative and paradigm-shifting position that carbon is not the primary consideration in climate; rather, it is water that should be a central focus in assessing climate processes and effects. It considers forests from a systems perspective.

Forest-driven water and energy cycles are poorly integrated into regional, national, continental and global decision-making on climate change adaptation, mitigation, land use and water management. This constrains humanity’s ability to protect our planet’s climate and life-sustaining functions. The substantial body of research we review reveals that forest, water and energy interactions provide the foundations for carbon storage, for cooling terrestrial surfaces and for distributing water resources. Forests and trees must be recognized as prime regulators within the water, energy and carbon cycles. If these functions are ignored, planners will be unable to assess, adapt to or mitigate the impacts of changing land cover and climate. Our call to action targets a reversal of paradigms, from a carbon-centric model to one that treats the hydrologic and climate-cooling effects of trees and forests as the first order of priority. For reasons of sustainability, carbon storage must remain a secondary, though valuable, by-product. The effects of tree cover on climate at local, regional and continental scales offer benefits that demand wider recognition. The forest- and tree-centered research insights we review and analyze provide a knowledge-base for improving plans, policies and actions. Our understanding of how trees and forests influence water, energy and carbon cycles has important implications, both for the structure of planning, management and governance institutions, as well as for how trees and forests might be used to improve sustainability, adaptation and mitigation efforts. [Ellison 2017: Abstract]

Ford 2017. Structural Complexity Enhancement (SCE) is part of a larger ecological concept: nature tends to complexity, providing its resiliency, flexibility and inventiveness. SCE in treatment of forests is a management approach that promotes development of late-successional structure, including elevated levels of coarse woody debris. It adds variety to tree ages (favoring older trees), and variations in available sunlight and habitat.

Large trees, previously assumed to slow in both productivity and growth rate (Weiner and Thomas 2001, Meinzer et al. 2011), function as long-term carbon sinks (Carey et al. 2001). These findings further support the significance of structural retention as a co-benefit to forest carbon storage. Adaptive silvicultural practices promoting multiple co-benefits, for instance, by integrating carbon with production of harvestable commodities, can contribute to efforts to dampen the intensity of future climate change while maintaining resilient ecosystems (Millar et al. 2007). Prescriptions that enhance in situ forest biomass and thus carbon storage offer one such alternative (Ducey et al. 2013). U.S. forests currently offset approximately 16% of the nation’s anthropogenic CO2 emissions, but this has the potential to decline as a result of land-use conversion and lack of management (EPA 2012, Joyce et al. 2014). While passive or low-intensity management options have been found to yield the greatest carbon storage benefit, assuming no inclusion of substitution effects (Nunery and Keeton 2010) or elevated disturbance risks (Hurteau et al. 2016), we suggest the consideration of SCE to enhance carbon storage. Multiple studies have explored co-benefits provided by management for or retention of elements of stand structural complexity, including residual large living and dead trees, horizontal variability, and downed CWM (Angers et al. 2005, Schwartz et al. 2005, Dyer et al. 2010, Gronewold et al. 2012, Chen et al. 2015). Silvicultural treatments can effectively integrate both carbon and late-successional biodiversity objectives through SCE based on this study and previous research (e.g., Dove and Keeton 2015). Remaining cognizant of the potential for old-growth compositional and structural baselines to shift over time and space with global change—climate impacts on forest growth and disturbance regimes, altered species ranges, and the effects of invasive species—will be important for adaptive management for late-successional functions such as carbon storage. [Ford 2017: 16]

Healing Harvest Forest Foundation. 

The spot compaction of animal feet is far less damaging to the forest soil and tree roots than the continuous track created by a wheel or track driven machine. Small sized tracts of timber can not be harvested with conventional methods that require higher capitalization and expensive moving cost.   The economic pressure in conventional forest harvesting operations influences most loggers to feel that they must cut all the trees to make their work cost effective.  This restricts the silvicultural prescriptions available for the management of the forest….Our method of selecting individual trees on a “worst first” basis and limiting removal to no more than 30% retains the forested condition and is indeed improvement forestry…. The holes created in the forest canopy are substantial enough for “shade intolerant” species to regenerate naturally from seedlings of the superior specimens that are left in a healthy “good growing” condition.  We believe that basically the repair of the forest from previous “high grading” is best accomplished through several successive “low grading” harvests. [Healing Harvest 1999]

Makarieva 2007.  The authors examine ecological and geophysical principles to explain how land far inland away from the ocean can remain moist, given that gravity continuously pulls surface and groundwater into the ocean over time.

All freshwater on land originates in the ocean from which it has evaporated, is carried on air flux, and precipitates over the land. Coastal regions benefit from this cycle by their proximity to the ocean, yet in the absence of natural forests in coastal regions precipitation weakens as distance from the ocean increases, leaving inland areas arid. The authors propose the concept of a biotic pump to explain how large continents can be sufficiently moist deep into the interior and abundant with rivers and lakes.

Air and moisture are pulled horizontally by evapotranspiration from coastal forests.  When water vapor from plants condenses, it creates a partial vacuum which pulls water evaporating from the ocean into the continental interior where it rains in forest.  By contrast, deserts are unable to pull ocean evaporation to them because they lack any evaporative force.

Such ongoing deforestation, and crucially coastal deforestation on a large scale, threatens to cut off rain to the interiors of Earth’s continents thereby creating new deserts. The Amazonian rainforest is the prime example.  Deforestation of the eastern coast of South America has led to changes in the rainforest that is resulting in drying and desertification of the interior, with unprecedented fires and loss of rivers.  Historically, Australia’s interior became a desert around the time the first humans arrived on the continent, and the authors speculate that early coastal deforestation was the cause. On the other hand, restoring natural coastal forests can also restore inland water cycles and reverse desertification.

This article illustrates the importance of biological relationships that are ecologically complex and poorly understood. It highlights the significance of the precautionary principle in assessing what we don’t know (and what we don’t know that we don’t know) when altering ecological processes, and taking preventive action in the face of uncertainty.