Tall multifamily buildings play a crucial role in reducing the environmental impact of each dwelling unit by concentrating those impacts in a smaller area than sprawling single-family developments. Studies have shown that per capita energy use, carbon emissions, and resource consumption in dense multifamily developments can be 30 to 50% lower, making dense urban living a more sustainable choice.

Additionally, dense development fosters pedestrian access to public transportation and proximity to local businesses and amenities, embodying the 15-minute city concept, which promotes a future where all essential services and amenities are within a 15-minute walk or bike ride from home—creating a convenient and sustainable lifestyle.

To build tall apartment buildings, constructors have relied on concrete and steel—extractive, mineral-based materials that undergo a complex transformation process. To become useful in the built environment, they must be pulverized, liquefied, transported, and processed with industrial heat. This transformation process imbues concrete and steel with high embodied energy, making them significant sources of CO2 emissions.

Cement production alone accounts for approximately 8% of global carbon dioxide emissions. The chemical reaction in the kiln releases CO2, and the high temperatures needed are usually achieved by burning coal. Steel production is also a significant emitter of CO2, primarily due to using coke (a coal derivative) in the blast furnace process. Overall, the embodied carbon of concrete and steel accounts for 22.7% of global CO2 emissions, most of which stem from buildings and infrastructure construction.

In response

In her new book, Designing the Forest and Other Mass Timber Futures, Lindsy Wikstrom presents a compelling argument for reducing our reliance on concrete and steel, advocating for using renewable, plant-based materials instead. Mass timber, a robust structural system made from engineered wood products, offers a sustainable alternative with a lower carbon footprint for buildings up to 18 stories tall. Sourced from renewable forests, mass timber combines the strength and durability required for tall buildings with the environmental benefits of a renewable resource, paving the way for a greener future in urban development.

An award-winning architect and professor at Columbia and Yale, Wikstrom founded Mattaforma, a New York–based architectural research and design firm. Designing the Forest grew from her research at Columbia, where she challenged her students with the question, “Can we build with mass timber in New York City?”

This inquiry led to extensive research into the history of forests, the timber industry, and current obstacles in mass timber construction. Over three years, Wikstrom immersed herself in every available publication on mass timber, forestry, and the supply chain of forest products. Her book’s plainspoken tone and instructive drawings are underpinned by academic rigor. Even if you disagree with her thesis, you’ll gain in-depth knowledge about trees and the transformation of forests into lumber.

Beyond mass timber buildings

Wikstrom advocates for a fundamental shift in how we conceive of forests and our relationship with them, viewing it as a coevolutionary bond of mutual sustainability. She explains: “What if I can get you out of the concrete and steel world and into mass timber, and then get you even further into this idea of what it means to design with biodiverse mass timber?”

Her argument is laid out in four sections: the urgency of developing sustainable buildings, the biology and bio-history of forests and our relationship with them, the current state of the forestry industry, and how we can shape a future where multi-species forests serve as carbon sinks that extend into the built environment.

Instead of making a moral argument for biodiversity, Wikstrom describes the fascinating web of mycelium tubes connecting diverse tree species in the forest, likening it to a biological fiber-optic network. She explains how species use these underground fungal networks to exchange nutrients: “In the summer, the surplus carbon collected by the leaves of the birch is shared with Douglas firs. In winter, when the birch has no leaves to feed itself, the fir shares its surplus.”

Additionally, older trees communicate with younger ones, teaching them to resist pests, drought, and fire. Drawing on well-documented biological studies, Wikstrom makes the economic case that biodiverse forests are more resilient in an era of climate change than are monocultures, which are more susceptible to diseases and environmental stressors like heat and drought.

Forest history, mass timber suitability

In “Inventing the Wilderness,” she dispels the romantic myth of natural and old-growth forests, explaining that very few forests remain unchanged by human hands. Since ancient times, humans have settled next to forests to extract wood for construction and fuel, cleared areas for agriculture, and then replanted with tree species to best meet their needs. Every forest you see has been harvested and replanted repeatedly, each time modeled by human hands.

In a curious example, Wikstrom explains how the OSB industry leveraged aspens, a “weed” tree, into the most cultivated species on the planet. Her recommendation in transforming silviculture is based on a balanced approach informed by cameralism and modern biological science, emphasizing the importance of achieving fair-trade economic benefits with ecological sustainability.

Following a tour-de-force of forest history, Wikstrom delves into the complete cycle of contemporary silviculture, from planting seedlings genetically engineered to resist local hazards to their selective harvest and use in creating mass timber products. These products combine fibers from various species to achieve specific levels and axes of strength.

Wikstrom devotes considerable space to dispelling myths about mass timber, such as its susceptibility to fire. Unlike steel, timber chars rather than melts, providing time for occupants to escape before a building collapses. (I attended the 2001 code hearings, where arguments against mass timber based on fire danger were thoroughly scrutinized and ultimately dismissed.) Wikstrom highlights that mass timber is now used for fireproofing steel building elements.

Additionally, she addresses concerns about polyurethane-reactive adhesives used to bind veneers and laminate boards, explaining they are nontoxic. And she points out that beef production causes more deforestation than the timber industry.

The human-forest interface

Wikstrom’s manifesto for the future postulates ways to add value to ecological concepts, such as the biodiversity of climax community forests, within a capitalist system by projecting economic benefits over the long term. She describes how ecologically maintained forests owned and cultivated by residents can provide a widely distributed source for mass timber projects, even in places like New York City.

The author decries the isolation of forests as islands cordoned off from urban areas and the separation of timberlands from wildlands, as practiced by the parks department and nature conservancies. She argues for a return to the forest-human interface.

Wikstrom also warns that 30% of our 60,000 tree species are in danger of extinction and that within the next 300 years, tropical forests will turn into savannas. This is good news for pioneer species like birch, poplar, and pine, which will benefit from a warmer, CO2-enriched climate, but bad news for more delicate varieties.

In 2011, the International Union for Conservation of Nature launched the Bonn Challenge, a global initiative to plant 860 million acres of forest by 2030. However, replacing slow hardwoods with fast-growing softwoods is transforming pledged areas into tree farms. In the short run, these dense, fast-growing species will provide a benefit in carbon sequestration; in the long run, reducing biodiversity and the presence of old growth risks the total loss of the forest. “If trees can’t remember how to fight off diseases or don’t have the same nutrient support from their neighbors, they are more likely to die,” explains Wikstrom.

She also cracks the illusion of sustainable forestry rating systems, such as the Forest Stewardship Council, explaining how free-trade liberalism makes it challenging to trace wood products from forest to lumberyard and how easy it is to forge a chain of custody. On the other hand, Wikstrom questions the ethics of framing certain harvest practices as illegal logging. “The application of this term is clearly biased, given that the global data is collected and collated by affluent nations who have positioned themselves as the progenitor of what forests should be, how they should be managed, and for what purpose,” she writes.

Economic incentives drive all harvests globally, so why are harvests in some regions labeled as unethical? In the future, blockchain technology may alter the way timber is tracked across great distances, given systems under development promise to guarantee wood’s geographical source within ½ km. Wikstrom believes a non-proprietary system not controlled or biased by one central authority will benefit stakeholders that wish to market virtuosity in forest management.

Final thoughts

Acknowledging a mass timber building’s susceptibility to moisture damage and natural biodegradation, Wikstrom completes the cycle from forest to high-rise with deconstruction. She writes, “All materials and assemblies age differently and need an attentive partner in occupants. Ultimately, the climate emergency is a waste-management problem. Designing for deconstruction aims to imbue buildings with details that can be demounted down the road, taken apart to be used again.”

While Wikstrom’s vision for a mass timber future may be challenging to implement on a large scale, her book provides a solid exposition of how wood is grown, sourced, transported, and used in construction. It argues for a sensitive, species-based methodology stewarded by architectural designers as “choreographers of carbon, transferring and trading between forest, factory, site, and beyond.”

I read the book twice, hoping to remember as much as possible about the nature of forests and the construction materials we extract from them. The book balances academic research with an accessible writing style that does not require a background in architecture, construction, or silviculture. It is a worthy read for anyone interested in deepening their appreciation of forests and the world we build with them.

However, it is an urgent and essential read for those engaged in architecture and construction who must learn about this new building method already changing how we design and construct the urban environment.

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Fernando Pagés Ruiz is a builder and an ICC-certified residential building inspector active in code development.