Healthy Forests, Wise & Wealthy Foresters

For the past 9,500 years, amid both natural and sociopolitical upheavals of colossal proportions, the global mean temperature has remained astoundingly steady. The latest measurements indicate that the mean has varied by no more than ±0.65°C since it first stabilized nearly 10 millennia ago. That this unique era of temperature stability has allowed humans to launch, develop, and sustain a global civilization, with a population now in the billions, is nothing short of a marvel. What we may have overlooked or underestimated until recently, however, is the crucial role Earth's forests play in maintaining this stability.

I grew up in British Columbia, a Canadian province some 40 percent larger than Texas and almost entirely covered by forest. During my time at the University of British Columbia, the forestry department was one of the largest anywhere. In fact, the university was founded on a land grant of more than six square miles so that the department of forestry could have an on-campus forest in which to conduct research.

If you've paid attention to the ongoing debate over global warming and climate change, you're aware that forests have become a major focus of attention. Climatologists are mobilizing efforts to alert the public that, of all terrestrial life, forests are the most efficient in removing greenhouse gases from the atmosphere, and they store the greatest quantity of carbon.

In other words, forests play a crucial role in holding back the rapid global temperature increase that, it is believed, currently threatens Earth's climate stability. No wonder climatologists argue for an all-out effort to preserve forests! We must be careful to note, however, that how we go about preserving forestsmakes an enormous difference in their impact on our climate. Some efforts to preserve forests can actually exacerbate global warming rather than mitigate it. Employing appropriate strategies is essential to effective mitigation. What I find additionally intriguing is that the most effective approaches also deliver the greatest economic benefits.

Tree Size Matters

The bigger the tree, the more carbon it stores. Although the largest trees in a typical forest constitute no more than ten percent of the total tree population, these trees store nearly 50 percent of the total carbon. They also provide extensive habitat for forest animals, especially birds and mammals, and capture moisture for the benefit of their larger ecosystem. For example, the California redwoods, the tallest trees on the planet, hold on to moisture from the layer of fog wafted in off the Pacific Ocean via westerly winds. This moisture accounts for up to half the forest area's total precipitation and makes possible a richer diversity of life than would be possible in an otherwise relatively arid region.

Large trees provide other benefits, as well. We find them majestic and awe-inspiring, and in this way they nourish our souls. They provide the comfort of shade and also limit the growth of ground-level shrubbery that would otherwise hinder animal and human navigation among them.

It's easy to see why conservationists tend to focus so much attention on preserving the largest trees in Earth's forests. Nevertheless, research reveals a complicating factor, one that requires a more sophisticated approach to forest management than simply protecting and preserving the largest trees. We cannot afford to ignore the environmental effects of trees' aging.

Tree Age Matters More

While the biggest trees in a forest appear to be the most invincible, they are not. They may be the most difficult to knock down, but they are actually the trees most at risk, not only to themselves but also to the rest of us.

Recent forest field studies show that the largest trees in a forest are, in fact, the ones most likely to be destroyed by lightning, drought, and pests. Research conducted in Panama by a team of ecologists led by Evan Gora and Steve Yanoviak indicates that in tropical forests, lightning accounts for 5.4 percent of medium-sized tree deaths, 2.9 percent of small-sized tree deaths, and 40.5 percent of large tree deaths.1 (For this study, the trees were grouped into size categories according to the diameter of their trunks.)

In another research study, forest ecologists Atticus Stovall, ­Herman Shugart, and Xi Yang conducted eight years of field studies across 40,000 hectares of forests in California's Sierra Nevada Mountains—forests subject to periodic droughts.2 The research team found that when droughts were not a factor, trees of all sizes died at approximately the same rate. However, during just one year of severe drought, roughly 40 percent of trees taller than 30 meters (100 feet) died, compared to only 28 percent of medium-sized trees and 16 percent of small trees.

Stovall, Shugart, and Yang identified two reasons for the taller trees' greater susceptibility to death during droughts. First, the taller the tree, the greater its difficulty in drawing up water to where most of its leaves (or needles) ­reside. Second, the taller the tree, the greater its susceptibility to attack by bark beetles as well as the pathogens those beetles carry.

Further investigation of trees' vulnerability to invasive pests was conducted in the eastern United States by forest ecologist Songlin Fei and his colleagues. Focusing specifically on hardwood trees, they discovered a direct correlation between the size of a tree and the likelihood of its death as a result of invading insects.3 Fei concluded that elderly trees lack the resources available to younger trees to help them recover from invasion and related pathogens.

In a fourth study, Australian forest ecologist David Lindenmayer noted, with no great surprise, that the largest trees are also the slowest to regrow after suffering damage.4 Their greater susceptibility to damage and slower regrowth and repair rate mean that the oldest and largest trees are the most challenging and costly to protect and preserve.

Optimized Forest Management

The most significant downside to all these findings about tree size is the recognition that dying and dead trees' ­decaying processes release large quantities of carbon dioxide (a greenhouse gas) into the atmosphere. Also, because even healthy large trees grow at a much slower rate than younger trees, they are far less effective, per unit of time, in removing carbon dioxide from the atmosphere.

For these reasons, a wise strategy for mitigating global warming and helping to maintain the stability of the global mean temperature would be to harvest the largest and oldest trees in a forest before they become unhealthy. Their wood could then be used to manufacture building materials and furniture, thereby safely sequestering the trees' carbon content for long periods of time.

Lindenmayer clarifies, however, that not all the largest trees in a forest should be harvested. As noted, the largest trees support a diverse ecosystem and help sustain the forest's microclimate. Harvesting all the large trees at once would put a forest's ecosystem at risk of collapsing. The collapse of forest ecosystems would, in turn, cause an increase in global warming.

On the other hand, banning all lumbering, as many environmentalists and climate change activists recommend, would also cause an increase in global warming. Thus, the most environmentally sound—and economically beneficial—strategy calls for harvesting the slowest-growing large trees while leaving a sufficient number of the healthiest and faster-growing large trees to sustain and enhance the forest ecosystem. This strategy must also ensure that two important controls are in place: (1) that the harvesting process retains the full diversity of tree species, and (2) that the age distribution of the trees being harvested maximizes the amount of carbon (per unit of time) removed from the atmosphere.

Alignment with Biblical Wisdom

I find it intriguing to note that the findings of these recent forest research studies beautifully illustrate a key biblical principle concerning wise management of Earth's resources. God has allowed us to discover, through our study of nature, a way to fulfill his command (Genesis 1, Job 37–39) to manage Earth's resources in a way that benefits all of Earth's life, human and non­human. We humans are not forced to choose between one management approach that is ecologically beneficial but economically deleterious and another that is economically beneficial but ecologically deleterious.

If we seek God's wisdom and diligently study creation in a spirit of humility, we can and will find strategies for maintaining the natural realm that are both economically and ecologically beneficial. In other words, God has designed the Earth and Earth's life in such a way that humans can fulfill the commands and purposes he intended.

1. Evan Gora and Stephen Yanoviak, from a lecture delivered at the August 2019 annual meeting of the Ecological Society of America, as reported by Elizabeth Pennisi, "Forest Giants Are the Trees Most at Risk," Science 365, no. 6457 (Sept. 6, 2019); Stephen P. Yanoviak et al., "Quantification and Identification of Lightning Damage in Tropical Forests," Ecology and Evolution 7, no. 14 (July 2017).
2. Atticus E. L. Stovall, Herman Shugart, and Xi Yang, "Tree Height Explains Mortality Risk During an Intense Drought," Nature Communications 10, no. 4385 (Sept. 26, 2019).
3. Songlin Fei et al., "Biomass Losses Resulting from Insect and Disease Invasions in US Forests," Proceedings of the National Academy of Sciences USA 116, no. 35 (Aug. 27, 2019).
4. David Lindenmayer, from a lecture delivered at the August 2019 annual meeting of the Ecological Society of America, as reported by Pennisi, "Forest Giants."

is an astrophysicist and the founder and president of the science-faith think tank Reasons to Believe (RTB).

This article originally appeared in Salvo, Issue #52, Spring 2020 Copyright © 2020 Salvo |