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Klaus Philipsen
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- #1
Why Forests Matter to the Climate
While I write this, New York, Baltimore, DC and large parts of the US are under a code red or purple air quality alert casting everything into an otherworldly light from pollution caused by smoke drifting south from massive Canadian wildfires. Another reason to think about forests, their benefits and the risks when they die.
Next to the oceans, forests are the planet's largest natural carbon sinks. At a time when efforts to reduce greenhouse gas emissions have stalled in many places, protecting and expanding carbon sinks has become even more important, yet protecting carbon sinks receives far less attention than reducing emissions. Architects, planners, and engineers need to pay attention.
Even though Earth's surface is 70% water, and forests cover only a portion of the landmass, they are estimated to account for around a quarter of annual global carbon dioxide absorption. But carbon capture is a complicated matter, especially when it comes to forests, so there is considerable uncertainty in the numbers. Forests both absorb and release carbon, making it difficult to determine their net contribution over time. In addition, when rainforests are removed, a chain reaction of additional effects can be set off. The exposure and destruction of the wet peatlands found beneath much of the shrinking Congo rainforest is one example. Peatlands hold enormous amounts of carbon, often in the form of methane. Once exposed—or, as in the case of melting permafrost, thawed—those wetlands and the forests above them are lost as carbon sinks and become carbon emitters instead.
Of course, forests are far more than emitters or absorbers of carbon. Depending on the type of forest or where they are located forests also provide habitat for other plants and animals, protect watersheds protection, filter water and air, and moderate temperature extremes.
This simple maxim raises an obvious question: how are forests doing locally, nationally, and globally? Are we gaining or losing forest cover?
As in many other aspects of climate change, the global—and even national—news is not encouraging. Just five countries—Russia, Brazil, Canada, the United States, and China, in that order—account for more than half of the world's total forest area, followed by the Congo Basin rainforest. Surprisingly, China is the only one of these countries to have achieved significant net forest gains over the past two decades. The issue becomes even more discouraging if one considers that not all forests are equal in their ability to counteract climate change and absorb carbon. Brazil has experienced the largest rain forest declines, the Congo Basin has also has seen extensive losses. Both are home to this most valuable type of forest. Brazilian rainforests are part of the Amazon which is the world's largest, rainforest, spanning 2.72 million square miles (roughly the size of the 48 contiguous United States), nearly two-thirds of it are located in Brazil. The Congo Basin spans 1.03 million square miles across six African countries (mostly in the DRC). Both Brazil and Congo still have a positiv carbon balance, though.
Before we point to those other far away countries, it is astonishing to realize that the United States has also failed to increase its forest cover despite a thicket of regulations intended to protect trees.
According to several databases, the United States shifted from annual net gains to annual net losses beginning around 2015. According to the UN Food and Agriculture Organization (FAO) Global Forest Resources Assessment, the net changes broke down as follows:
Forest losses result from a combination of commercial logging, development, agriculture, natural disturbances such as insect infestations, disease, drought, coastal erosion and saltwater intrusion, tree mortality and, increasingly, wildfires. The losses and gains vary considerably among countries and among U.S. states. Not all countries or states maintain consistent databases, and much of the analysis is conducted by international organizations using satellite imagery, which has inherent limitations. For example, satellite data cannot easily distinguish between old-growth and second-growth forests or identify invasive species that may be degrading forest health.
In the United States, Alaska and California appear to have suffered the greatest forest losses, primarily because of wildfires. Georgia and Alabama are centers of commercial forestry, where harvest and reforestation alternate as part of normal timber production cycles. Northeastern states such as Vermont, New Hampshire, Maine, and New York have recorded net forest gains over much of this twenty-five-year period. Drivers include reforestation policies, abandoned farmland returning to forest, and strong tree conservation and replacement requirements in local development ordinances.
Forest health is not just a numbers game, it is also a function of forest management. A resilient forest needs intervention, especially in light of increasing imbalances in the natural ecosystems. In the US those imbalances include excessive deer populations, invasive vines such as kudzu which can suffocate entire woods and increased tree mortality from excessive temperatures. Fragmentation does not make a resilient forest. It is neither good for wildlife nor for effective forest management.
Developers, engineers, architects, builders, and planners share responsibility for fragmentation and the loss of forests to development thanks to poor land use regulations and excessive sprawl. As an architect I will focus on those aspects in this article.
For people working in construction and development, trees are often a building material with which increasingly bigger structures are framed and constructed. Still, trees and sometimes forests are also part and parcel of land use, infrastructure and aesthetics. In new construction, though, existing vegetation is too often seen as an obstacle. Then trees are felled to make space for development, no matter that regulations often require new tree planting to offset removals or that the new spindly trees will take many years before they create the benefits of the felled mature trees.
When trees are used as a raw material for structures and finishes, heavy timber can be an important carbon-storage strategy, the longer the wood is in use, the more so. This is why wood in construction should always be recycled for future use when a structure is demolished or when it only used for formwork, shoring, or temporary structures. Wood that is not recycled accounts for a significant share of the overall waste, and will eventually emit its stored carbon whether in an incinerator or in a landfill. Using more wood in construction does not necessarily mean less forest cover or greater carbon emissions. Quite the opposite. Even rapidly growing commercial tree plantations absorb carbon that is kept in buildings as long as the wood stays in the buildings or is responsibly reused while trees grow back quickly. Forests that provide an economic benefit also provide the resources to manage them.
In short, the touchpoints between forests, trees and development are numerous, affecting both carbon emissions and carbon capture.
Just as forests are not only about carbon, individual trees can also have numerous benefits, from increasing property values through aesthetics and better curb appeal to improving air quality, reducing the heat island effect, and enhancing the neighborhood character. The "leafy" neighborhoods are usually the ones with the more expensive homes.
Still, homeowners, developers and builders have a very ambiguous relationship to trees, seeing them as a risk factor for homes, parked cars or people or as an added maintenance item (leaves in the fall). Ironically, trees indeed are posing increasing risks to structures, the more climate change intensifies. Stronger storms knock more trees on to structures, or trees become fuel for ever stronger fires.
The objective should be to locate and manage trees intelligently through proper species selection, adequate setbacks from structures, and a site design that is responsive to specific local risks. The optimum of benefits and risks varies greatly by site geography.
Overall, there can be no question that the more trees there are and the greater forest cover there is, the better the outcome for a property, the local micro climate and the global climate. The value of mature trees lining streets, shading buildings, stabilizing soils, and absorbing stormwater far exceeds the risks associated with falling limbs or their potential contribution to wildfire fuel.
In the United States, strict regulations regarding trees and forests are common, ranging from the protection of specimen trees to mandatory tree replacement requirements, especially in areas where stream erosion or water quality are major concerns, such as the Critical Area zones of the Chesapeake Bay. Many municipalities also require minimum landscaping standards. Many cities aim for 50% or so tree coverage or want to become "sponge cities" to combat summer heat and floods. Atlanta has already reached the tree coverage goal. It is truly astounding how green neighborhoods look there when seen from the vantage point of a downtown office tower.
Still, even where strict ordinances exist, development is cheaper on farms and forests than on grey-fields, brownfields or by densifying existing neighborhoods. Local zoning and land use plans all too often yield to developers, engineers, and builders who dream of level, obstacle-free, bulldozed development parcels. As a result the "development community" continues to cut down forests contributing to the net forest loss that we see in many states of the US. Short-term thinking causes initial construction costs to outweigh the long-term benefits of higher resale values, water conservation, reduced heating and cooling loads, and improved quality of life for residents—not to mention the health of the planet.
Regulations are also rapidly adjusting for where wood can used as a structural material. Most states now allow heavy timber construction even for midrise buildings, sometimes even high-rises. Wood as a framing material is now allowed for sometimes six-story buildings if they sit on a concrete podium.
Trees are living things, of course and as such there are also ethics-based legislative initiatives underway to give trees rights as part of a movement that gives "nature" rights. A Universal Declaration on the Rights of Trees was drafted in France in 2018 by lawyers, ecologists and lawmakers. It mandates that humanity “act with the Tree in a spirit of fraternity and solidarity” and has been presented as a petition to the United Nations and the European Parliament, among others. The small town of Vaudreuil in Canada is considering its adoption. Will future generations look at the nonchalance in which we relegate trees to chippers turning them into nothing more valuable than mulch, as practice comparable to killing buffalo for their hides or elephants for their tusks? Hard to know.
Luckily attitudes towards wood and woods are changing generally, one could say, we have come full circle. Wood was once such a common and readily available construction material that builders, architects, and engineers were intimately familiar with local species, their density, hardness, and structural properties, as well as their value as fuel. Where forests were abundant, wood traditionally became the material of choice for residential construction, giving buildings a distinct, authentic character.
But modern construction, invasive species, international trade, engineered wood products, and the widespread use of plastics have all contributed to decades of diminished awareness of the role wood can play. With climate change becoming increasingly urgent and many people tired of soulless drywall boxes, mass timber construction has gained popularity. Wood is once again being recognized as a sophisticated, high-performance construction material, and knowledge about sustainably harvested timber is growing along with the rising demand for wood. The advantages of wood for efficient construction and operation as well as occupant well-being are becoming increasingly apparent.
Computer based detailed life-cycle carbon analyses now available to architects and engineers interested in sustainable design demonstrate that the use of sustainably harvested wood can produce a positive carbon balance, provided buildings are designed to allow reuse of wood after the end of their initial life cycle.
Science is uncovering more and more insights about trees as part of a complex ecosystem in which trees "communicate" and support each other in a "wood-wide-web. The New York Times recently reported about the "Social Life of Forests".
Architects, planners and engineers, can no longer treat forests merely as obstacles on development or as sources of building materials. Forests are part of the planet's climate infrastructure. Every decision to preserve mature trees, design around existing forests, specify sustainably harvested timber, or design buildings for future material reuse not only benefits a particular project but contributes to saving one of our most effective natural climate solutions
Klaus Philipsen, FAIA
related on this blog:
Time to Abandon the Scorched Earth Approach in Subdivision Development
The Timber Revolution
How One Plus Five is Shaping American Cities
While I write this, New York, Baltimore, DC and large parts of the US are under a code red or purple air quality alert casting everything into an otherworldly light from pollution caused by smoke drifting south from massive Canadian wildfires. Another reason to think about forests, their benefits and the risks when they die.
Next to the oceans, forests are the planet's largest natural carbon sinks. At a time when efforts to reduce greenhouse gas emissions have stalled in many places, protecting and expanding carbon sinks has become even more important, yet protecting carbon sinks receives far less attention than reducing emissions. Architects, planners, and engineers need to pay attention.
[td]
[/td]
[td]
Puerto Rican rain forest (Photo: Philipsen)
[/td]Even though Earth's surface is 70% water, and forests cover only a portion of the landmass, they are estimated to account for around a quarter of annual global carbon dioxide absorption. But carbon capture is a complicated matter, especially when it comes to forests, so there is considerable uncertainty in the numbers. Forests both absorb and release carbon, making it difficult to determine their net contribution over time. In addition, when rainforests are removed, a chain reaction of additional effects can be set off. The exposure and destruction of the wet peatlands found beneath much of the shrinking Congo rainforest is one example. Peatlands hold enormous amounts of carbon, often in the form of methane. Once exposed—or, as in the case of melting permafrost, thawed—those wetlands and the forests above them are lost as carbon sinks and become carbon emitters instead.
Of course, forests are far more than emitters or absorbers of carbon. Depending on the type of forest or where they are located forests also provide habitat for other plants and animals, protect watersheds protection, filter water and air, and moderate temperature extremes.
[td]
[/td]
[td]
Sri Lankan forest & habitat (Photo: Philipsen)
[/td]How Are Forests Doing—Globally, Nationally, and Locally?
This simple maxim raises an obvious question: how are forests doing locally, nationally, and globally? Are we gaining or losing forest cover?
As in many other aspects of climate change, the global—and even national—news is not encouraging. Just five countries—Russia, Brazil, Canada, the United States, and China, in that order—account for more than half of the world's total forest area, followed by the Congo Basin rainforest. Surprisingly, China is the only one of these countries to have achieved significant net forest gains over the past two decades. The issue becomes even more discouraging if one considers that not all forests are equal in their ability to counteract climate change and absorb carbon. Brazil has experienced the largest rain forest declines, the Congo Basin has also has seen extensive losses. Both are home to this most valuable type of forest. Brazilian rainforests are part of the Amazon which is the world's largest, rainforest, spanning 2.72 million square miles (roughly the size of the 48 contiguous United States), nearly two-thirds of it are located in Brazil. The Congo Basin spans 1.03 million square miles across six African countries (mostly in the DRC). Both Brazil and Congo still have a positiv carbon balance, though.
Before we point to those other far away countries, it is astonishing to realize that the United States has also failed to increase its forest cover despite a thicket of regulations intended to protect trees.
[td]
[/td]
[td]
Forest removal for a subdivision in MD (Photo: Philipsen)
[/td]According to several databases, the United States shifted from annual net gains to annual net losses beginning around 2015. According to the UN Food and Agriculture Organization (FAO) Global Forest Resources Assessment, the net changes broke down as follows:
Causes of Forest Loss
Forest losses result from a combination of commercial logging, development, agriculture, natural disturbances such as insect infestations, disease, drought, coastal erosion and saltwater intrusion, tree mortality and, increasingly, wildfires. The losses and gains vary considerably among countries and among U.S. states. Not all countries or states maintain consistent databases, and much of the analysis is conducted by international organizations using satellite imagery, which has inherent limitations. For example, satellite data cannot easily distinguish between old-growth and second-growth forests or identify invasive species that may be degrading forest health.
In the United States, Alaska and California appear to have suffered the greatest forest losses, primarily because of wildfires. Georgia and Alabama are centers of commercial forestry, where harvest and reforestation alternate as part of normal timber production cycles. Northeastern states such as Vermont, New Hampshire, Maine, and New York have recorded net forest gains over much of this twenty-five-year period. Drivers include reforestation policies, abandoned farmland returning to forest, and strong tree conservation and replacement requirements in local development ordinances.
Forest health is not just a numbers game, it is also a function of forest management. A resilient forest needs intervention, especially in light of increasing imbalances in the natural ecosystems. In the US those imbalances include excessive deer populations, invasive vines such as kudzu which can suffocate entire woods and increased tree mortality from excessive temperatures. Fragmentation does not make a resilient forest. It is neither good for wildlife nor for effective forest management.
[td]
[/td]
[td]
Gains and losses of forest in PA (Pennsylvania Hardwood Council)
[/td]Developers, engineers, architects, builders, and planners share responsibility for fragmentation and the loss of forests to development thanks to poor land use regulations and excessive sprawl. As an architect I will focus on those aspects in this article.
When the Forest Becomes Wood
For people working in construction and development, trees are often a building material with which increasingly bigger structures are framed and constructed. Still, trees and sometimes forests are also part and parcel of land use, infrastructure and aesthetics. In new construction, though, existing vegetation is too often seen as an obstacle. Then trees are felled to make space for development, no matter that regulations often require new tree planting to offset removals or that the new spindly trees will take many years before they create the benefits of the felled mature trees.
When trees are used as a raw material for structures and finishes, heavy timber can be an important carbon-storage strategy, the longer the wood is in use, the more so. This is why wood in construction should always be recycled for future use when a structure is demolished or when it only used for formwork, shoring, or temporary structures. Wood that is not recycled accounts for a significant share of the overall waste, and will eventually emit its stored carbon whether in an incinerator or in a landfill. Using more wood in construction does not necessarily mean less forest cover or greater carbon emissions. Quite the opposite. Even rapidly growing commercial tree plantations absorb carbon that is kept in buildings as long as the wood stays in the buildings or is responsibly reused while trees grow back quickly. Forests that provide an economic benefit also provide the resources to manage them.
In short, the touchpoints between forests, trees and development are numerous, affecting both carbon emissions and carbon capture.
Just as forests are not only about carbon, individual trees can also have numerous benefits, from increasing property values through aesthetics and better curb appeal to improving air quality, reducing the heat island effect, and enhancing the neighborhood character. The "leafy" neighborhoods are usually the ones with the more expensive homes.
[td]
[/td]
[td]
Tree lined residential street in Baltimore
(Photo: Philipsen)
[/td](Photo: Philipsen)
Still, homeowners, developers and builders have a very ambiguous relationship to trees, seeing them as a risk factor for homes, parked cars or people or as an added maintenance item (leaves in the fall). Ironically, trees indeed are posing increasing risks to structures, the more climate change intensifies. Stronger storms knock more trees on to structures, or trees become fuel for ever stronger fires.
The objective should be to locate and manage trees intelligently through proper species selection, adequate setbacks from structures, and a site design that is responsive to specific local risks. The optimum of benefits and risks varies greatly by site geography.
Overall, there can be no question that the more trees there are and the greater forest cover there is, the better the outcome for a property, the local micro climate and the global climate. The value of mature trees lining streets, shading buildings, stabilizing soils, and absorbing stormwater far exceeds the risks associated with falling limbs or their potential contribution to wildfire fuel.
Regulations
In the United States, strict regulations regarding trees and forests are common, ranging from the protection of specimen trees to mandatory tree replacement requirements, especially in areas where stream erosion or water quality are major concerns, such as the Critical Area zones of the Chesapeake Bay. Many municipalities also require minimum landscaping standards. Many cities aim for 50% or so tree coverage or want to become "sponge cities" to combat summer heat and floods. Atlanta has already reached the tree coverage goal. It is truly astounding how green neighborhoods look there when seen from the vantage point of a downtown office tower.
[td]
[/td]
[td]
from a downtown tower the Atlanta neighborhoods
look all green (Photo: Philipsen)
[/td]look all green (Photo: Philipsen)
Still, even where strict ordinances exist, development is cheaper on farms and forests than on grey-fields, brownfields or by densifying existing neighborhoods. Local zoning and land use plans all too often yield to developers, engineers, and builders who dream of level, obstacle-free, bulldozed development parcels. As a result the "development community" continues to cut down forests contributing to the net forest loss that we see in many states of the US. Short-term thinking causes initial construction costs to outweigh the long-term benefits of higher resale values, water conservation, reduced heating and cooling loads, and improved quality of life for residents—not to mention the health of the planet.
Regulations are also rapidly adjusting for where wood can used as a structural material. Most states now allow heavy timber construction even for midrise buildings, sometimes even high-rises. Wood as a framing material is now allowed for sometimes six-story buildings if they sit on a concrete podium.
Trees are living things, of course and as such there are also ethics-based legislative initiatives underway to give trees rights as part of a movement that gives "nature" rights. A Universal Declaration on the Rights of Trees was drafted in France in 2018 by lawyers, ecologists and lawmakers. It mandates that humanity “act with the Tree in a spirit of fraternity and solidarity” and has been presented as a petition to the United Nations and the European Parliament, among others. The small town of Vaudreuil in Canada is considering its adoption. Will future generations look at the nonchalance in which we relegate trees to chippers turning them into nothing more valuable than mulch, as practice comparable to killing buffalo for their hides or elephants for their tusks? Hard to know.
The Changing Attitudes Toward Wood
Luckily attitudes towards wood and woods are changing generally, one could say, we have come full circle. Wood was once such a common and readily available construction material that builders, architects, and engineers were intimately familiar with local species, their density, hardness, and structural properties, as well as their value as fuel. Where forests were abundant, wood traditionally became the material of choice for residential construction, giving buildings a distinct, authentic character.
[td]
[/td]
[td]
Under Armour store, mass timber construction
(Photo: Philipsen)
[/td](Photo: Philipsen)
But modern construction, invasive species, international trade, engineered wood products, and the widespread use of plastics have all contributed to decades of diminished awareness of the role wood can play. With climate change becoming increasingly urgent and many people tired of soulless drywall boxes, mass timber construction has gained popularity. Wood is once again being recognized as a sophisticated, high-performance construction material, and knowledge about sustainably harvested timber is growing along with the rising demand for wood. The advantages of wood for efficient construction and operation as well as occupant well-being are becoming increasingly apparent.
Computer based detailed life-cycle carbon analyses now available to architects and engineers interested in sustainable design demonstrate that the use of sustainably harvested wood can produce a positive carbon balance, provided buildings are designed to allow reuse of wood after the end of their initial life cycle.
Science is uncovering more and more insights about trees as part of a complex ecosystem in which trees "communicate" and support each other in a "wood-wide-web. The New York Times recently reported about the "Social Life of Forests".
Architects, planners and engineers, can no longer treat forests merely as obstacles on development or as sources of building materials. Forests are part of the planet's climate infrastructure. Every decision to preserve mature trees, design around existing forests, specify sustainably harvested timber, or design buildings for future material reuse not only benefits a particular project but contributes to saving one of our most effective natural climate solutions
Klaus Philipsen, FAIA
related on this blog:
Time to Abandon the Scorched Earth Approach in Subdivision Development
[td]
[/td]
[td]
Barren subdivision, WVa
[/td]The Timber Revolution
[td]
[/td]
[td]
Wood construction in stadium design (Fukushima via
Dezeen)
[/td]Dezeen)
How One Plus Five is Shaping American Cities