Life in the Concrete Jungle: The Importance of Urban Biodiversity

Urban biodiversity refers to the variety of life forms—plants, animals, fungi, and microorganisms—that exist within urban areas like cities and towns. These organisms coexist in both natural and built environments and adapt to human-dominated landscapes, encompassing everything from the wildlife living in parks and green spaces to species inhabiting more developed environments, such as streets, rooftops, and even buildings. Biodiversity and ecosystems outside the city have a profound impact on the quality of life in urban areas with crucial connections to air and water quality, climate regulation, mental and physical health, and biodiversity spillover.

Source: Fisher, P. August 29, 2019. “Extinction debt: Urban biodiversity may be the answer.” Independent Australia. Available at: https://independentaustralia.net/environment/environment-display/extinction-debt-urban-biodiversity-may-be-the-answer,13054

Biodiversity supports human wellbeing in urban areas. At the same time, urbanization profoundly affects biodiversity. As cities expand, natural habitats are destroyed or fragmented, making it harder for species to find suitable places to live and reproduce. Fragmentation reduces genetic diversity and limits access to resources like food and water. Further, urban areas produce various forms of pollution, including air, water, and noise pollution, which can harm species, especially those sensitive to changes in their environment. Cities also contribute to climate change by increasing greenhouse gas emissions and associated climate change, which disrupts ecosystems and alters habitats. The movement of people and goods can introduce non-native species to urban environments, sometimes outcompeting local species and disrupting ecosystems. Despite these challenges, cities can also host surprising levels of biodiversity if the urban landscape is managed thoughtfully, with green spaces like parks, community gardens, and green roofs supporting both native and non-native species.

To prioritize sustainability, biodiversity, and ecological health, ecological planning can be used as a framework for designing cities and landscapes. Ecological planning involves understanding and integrating natural systems and processes into the development of urban areas and ensuring that ecological values are maintained or enhanced even as cities grow. This kind of ecosystem-centered planning process can be an essential tool for creating equitable access to green spaces by identifying and protecting natural areas, particularly in underserved communities, and making sure that green spaces are distributed fairly across the city. Ecological planning can also be used to develop multi-functional spaces, involving the local communities in the design and management of green spaces. Plans can incorporate green infrastructure, such as green walls, urban forests, and permeable pavements, which can enhance biodiversity within urban areas while providing essential services like stormwater management, air purification, and heat mitigation. These types of green interventions can be strategically placed in historically marginalized neighborhoods to improve the quality of life for all residents. By supporting urban biodiversity, interventions can both enrich the ecosystems within cities and strengthen the vital connection between urban areas and the broader natural environment.

Alicia Zhang

Research Fellow

This is a part of the AEC Blog series.

Engineering Challenges of Integrating Renewables to the Power Grid

Simply put, the electric power grid delivers or transmits electricity from a generation station, such as a wind turbine or solar photovoltaic (PV) panel, to customers, undergoing stages that include regional transmission, voltage increases and reductions, and local distribution. After leaving the generating station, electricity enters a sub-station where a step-up transformer raises the voltage to extremely high levels to allow for long-distance transmission. High-voltage electricity is then transferred to local substations, where a step-down transformer reduces voltage to levels suitable for customer use. Distribution lines carry this lower-voltage electricity from local substations to customer homes and businesses. Energy electric generation and battery storage that are located at the site of a home or business are called “distributed” or “behind-the-meter” systems. Rooftop solar and other behind-the-meter resources can help reduce reliance on grid-based power plants and on the transmission infrastructure needed to distribute electricity across long distances.

*Source: Stanford University. N.d. The Grid: Electricity Transmission, Industry, and Markets. Available at:* *https://understand-energy.stanford.edu/energy-currencies/electricity-grid*

As renewable energy gets integrated into this grid system, several engineering benefits and challenges can arise. Wind turbines, which generated 10.25 percent of the total U.S. power supply in 2022, convert wind energy into electricity by rotating blades to spin a generator. One of the benefits of turbines is that, after being disconnected from the energy source, they keep spinning with inertia for some time. This lag provides operators with time to address system failures before total loss of power.

One of wind energy’s biggest engineering challenges, however, is designing turbine blades to efficiently extract energy from air. Predicting the flow of air around an object is challenging, and the blades must withstand the stress they are subject to while rotating. In addition, the strength of the wind cannot be controlled to increase or decrease power generation as needed. Wind energy is typically transported from sparsely populated open areas where the wind blows more easily, to dense urban areas with high demand for power. The longer the distance from electric customers, the more electricity is lost from the lines.

Solar PV panels absorb sunlight through conductive metal contact lines on the solar panels. The energy then flows through the panels as an electrical current, delivering power to the home, businesses, or electric grid. Solar panels can be deployed at a small scale close to areas of customer electric demand, such as on the rooftops of residential homes.

Solar cells are not, however, very efficient, converting just 20 percent of the sunlight they absorb into electric power. Furthermore, solar cells produce direct current (DC) electricity, which means that the electrical current flows in only one direction within the circuit. Most home and commercial electric use—such as lights and appliances—requires alternating current (AC) electricity. Solar energy must be converted from DC to AC using an inverter before it can be integrated into the electrical grid or used in homes and businesses.

On very windy or very sunny days, renewables can overproduce electricity resulting in spikes in electric production that can cause issues controlling frequency and voltage on the grid. Both are important characteristics for a functioning electric system. Aging transmission lines and substations might not be able to handle the energy spikes, increasing risks of outages, or may require disconnecting energy generators to avoid system-wide problems. Surplus electricity can be stored in batteries and later released, reducing the risk of system outages during periods of low production. “Smart grid” technologies, such as advanced metering and automated control systems, can help monitor grid stability in real-time, optimize power flow, and predict outages. Relocating transmission wires underground or upgrading poles and wires to sturdier materials can make the electric grid more resistant to damage from severe weather or other threats. These strategies—storage, smart grids, and infrastructure upgrades—enhance grid resilience, reliability, and stability for a clean energy future.

Alicia Zhang

Research Fellow

This is a part of the AEC Blog series.

What Is Climate Financing and Why Do We Need More of It?

Image Source: Browne, K. 2021. *Advancing Equity in International Climate Finance: New Approaches to Informal Institutions and Power.* Available at: https://deepblue.lib.umich.edu/bitstream/handle/2027.42/169654/kebr_1.pdf

Climate finance refers to the flow of funds from public, private, or alternative sources of funding for local, national, or transnational activities or programs that are intended to help address climate change. Significant financial resources are necessary to design and implement large-scale climate mitigation and adaptation investments.

To this end, the Biden Administration has established the Inflation Reduction Act (IRA), which provides nearly $400 billion in loans and grants to fund projects to lower the nation’s carbon emissions. These projects include—among many other categories—funding states’ energy efficiency programs, restoring ecosystems on public lands, and incentivizing funding for low carbon materials used in transportation. IRA funding supports the nation’s goal of halving U.S. greenhouse gas emissions from 2005 levels by 2030, and achieving a net-zero emissions economy by 2050.

There are many avenues from which climate funding flows. Financing can flow from one country or institution to another (“bilateral”) or from many countries/institutions to another (“multilateral”). The funding source also varies. For example, governments can issue sovereign green bonds, which are loans from a pool of investors in exchange for regular interest payments over a set number of years, or from carbon trading and/or carbon taxes. On the international level, countries or financial institutions like the World Bank, Green Climate Fund, or USAID provide grants and loans.

Along with the IRA, the United States has made it a goal through its Justice40 Initiative that 40 percent of federal climate investments flow to disadvantaged communities that have historically been underinvested and overburdened by pollution. Although the United Nations Framework Convention on Climate Change (UNFCCC) enshrines equity as a core principle in climate action, equity has failed to be upheld in the international climate finance realm. To uphold equity would require that countries with more historic responsibility for climate impacts primarily due to heavily polluting industrialization and who also have a greater financial capacity, to act as “Donor Countries” and provide those with lower levels of responsibility and capacity with climate financing. While it has made great strides with the IRA on the domestic level, the United States is one such country, along with E.U. nations, Japan, and Australia, whose climate financing responsibilities extend beyond national borders.

The amount of finance needed to meet climate goals ranges from $600 billion per year up until 2030 to $1 trillion per year by 2025, and $2.4 trillion per year from 2030. International political negotiations have determined a $100 billion a year goal for 2020, but this goal was not met and extended to 2025.

Developing countries are not getting the funding that they were promised by developed countries. In fact, in 2021, developing nations received 15 percent less money for climate adaptation that the year prior. In total, developed countries received only $21.3 billion in public funding in 2021. Private financing can perhaps fill this gap – however, the lack of effective carbon pricing reduces the incentive and ability of investors to fund climate projects, as does incomplete climate data and disclosure standards. Private climate financing amounted to $14.4 billion in 2021, but this level of funding has been stagnant since 2017.

To meet climate goals, developed nations, including the United States, must scale up their efforts to both provide financing and to mobilize private financing. Nations can focus on developing policies that redirect investment flows from high-carbon projects to climate friendly opportunities, strengthen the climate information architecture, and support innovative financial structures that support the creation of new markets for climate finance.

Alicia Zhang

Research Fellow

This is a part of the AEC Blog series.

The Inflation Reduction Act is Investing in Nuclear. Should It?

Source: Jacoby, M. March 30, 2020. “As nuclear waste piles up, scientists seek the best long-term storage solutions.” Chemical & Engineering News. Available at: https://cen.acs.org/environment/pollution/nuclear-waste-pilesscientists-seek-best/98/i12

The Inflation Reduction Act (IRA) of 2022 is a $780 billion federal effort to stimulate the economy and advance U.S. infrastructure through tax breaks and other incentives. With almost half of the IRA funding dedicated to climate actions, a key goal of the IRA is to address the climate crisis by generously funding clean energy, climate mitigation, agriculture, and conservation-related programs. The IRA exclusively set aside $700 million for nuclear research, and nuclear infrastructure projects are eligible for $250 billions worth of loans, amongst several tax credits.

Nuclear has long been an important energy source. Electric generation from nuclear facilities results in no direct carbon emissions and is the most efficient and reliable energy source, according to the U.S. Department of Energy. It is currently the largest source of clean power in the U.S., producing more than half of U.S. carbon-free electricity. The nuclear industry also supports half a million jobs and contributes $60 billion to the nation’s gross domestic product each year.

The IRA supports nuclear energy by both providing a tax break and funds to support nuclear facilities and research. The IRA provides financing for some nuclear energy facilities and has allocated hundreds of millions of dollars to support research on fuel (high-assay low-enriched uranium), particularly for commercial use. While there is no direct allocation of funds towards existing nuclear plants, the IRA has also appropriated $150 million to the Office of Nuclear Energy (ONE) to assist with advanced reactor projects and oversight of the existing nuclear fleet and infrastructure. The IRA also provides a tax break, in the form of a Production Tax Credit (PTC) for qualifying nuclear facilities, including those that already exist. In an effort to prevent existing facilities from closing, these facilities can receive credit for each kilowatt hour (kWh) of electricity produced. The ONE claims that the IRA-funded PTC is a “game changer for nuclear energy” as it helps “preserve the existing fleet of nuclear plants.”

IRA funding for nuclear supports the mining of uranium, as well as the eventual disposal of its radioactive waste. Radioactive nuclear waste is unstable and poses health risks for thousands of years. High doses of radiation lead to health risks, such as cardiovascular disease and cancer, or even radiation sickness and death at very high doses. Radioactive waste also affects the local ecosystem through thermal pollutions during the cooling process, the release of toxins and degradation of habits from surface mining, and DNA damage to marine species due to radioactive leakages from waste disposal.

The United States has accumulated over 85,000 metric tons of waste from spent nuclear fuel from commercial nuclear power plants that have no clear designation for permanent disposal. This waste has been temporarily disposed, mostly in Illinois, Pennsylvania, and South Carolina (Figure 1). The amount of nuclear waste grows by about 2,000 metric tons a year, and it is anticipated that the federal government will pay tens of billions of dollars in the coming decades in damages to utilities for failing to dispose of this waste, on top of the billions of dollars already paid. Without a permanent, regulated, and maintained disposal site, the safety of continued and potentially expanded nuclear energy production is questionable.

Disproportionate dispersion of the burdens of hosting uranium mines and nuclear waste storage facilities can lead to environmental injustices. Low-income and minority communities are disproportionately targeted with nuclear facilities and waste disposal sites. Radioactive waste from spent uranium fuel particularly harm frontline communities - which are often Indigenous, of color, poor, and rural - due to both proximity, lack of resources, and racial and class discrimination.

With nuclear qualifying for PTC, amongst other funding opportunities, the IRA recognizes the potential for nuclear power plants to provide a low-carbon source of electricity by increasing incentives to produce nuclear-generated electricity. As such, the IRA acknowledges that nuclear plants have played and continue to play a significant role in the nation’s clean energy transition, despite the controversy surrounding them. Nuclear certainly has the potential to provide a substantial amount of clean energy to the nation, but the questions arise: “at what cost” and “to whom”? Plans to continue and potentially expand the U.S. nuclear fleet must carefully consider how uranium is extracted and where the waste will end up, to ensure that the clean energy transition is also just.

Alicia Zhang

Research Assistant

This is a part of the AEC Blog series

Mis/Disinformation: A Climate of Deceit

Source: McNutt, M. 2022. Misinformation: addressing the challenge. Proceedings of the Indian National Science Academy, 88, 8150821. https://doi.org/10.1007/s43538-022-00122-0

Since the late 1980s, fossil fuel corporations have engaged in mis- and disinformation by adamantly denying that human activity has caused climate change. In 1989, ExxonMobil publicly stated that “enhanced greenhouse is still deeply imbedded in scientific uncertainty,” and even established the Global Climate Coalition to question the scientific basis for climate change.

Misinformation and disinformation are closely related, but separate concepts. Misinformation is the sharing of information that is false or incorrect. Disinformation is the deliberate spread of misinformation with the intent to mislead. False information can generally be categorized by three broad buckets: (1) outright denial that climate change is occurring, (2) cherry-picking, in which certain data are selected to give a false image, and (3) providing false solutions. Illustrations of misinformation includes “climate change is not real and/or is not related to human activities” or “renewables and electric vehicles are useless or dangerous.”

In an urgent time to transition to clean energy, misinformation is hindering renewable energy projects across the United States. Some communities have become suspicious about clean energy projects, challenging local engagement. Recently, in October 2023, climate scientists and fossil fuel industry supporters have clashed in Texas over whether the association between climate change and human activities should be included in middle school textbooks.

Climate action is one of the 17 Sustainable Development Goals set by the United Nations. To combat mis/disinformation, climate change information, together with its sources, should always be carefully assessed for accuracy and trustworthiness, especially if the information targets scientists personally and generally denies climate science. Any person who is referenced in the report should be an expert on the subject, and the information provided should not selectively exclude any details.

Alicia Zhang

Research Assistant

This is a part of the AEC Blog series

Migration in a Climate-Changed World

Human migration due to climate change impacts, such as floods, heat waves, droughts, and wildfires, is on the rise.

Climate change is exerting increasing pressure on people throughout the world, especially Indigenous, people of color, and low-income groups, coastal communities, and those reliant on agriculture. Historically, Mexican migration to the United States has spiked during periods of drought. By 2080, climate change could drive 6.7 million more people to the Southern U.S. border. Drought pushed Syrians into cities, exacerbating tensions and discontent before the ongoing civil war, which has lasted more than a decade. Unemployment, inflation due to agricultural prices, and rapid urbanization due to crop losses were important stressors that helped stoke Arab Springs in Egypt and Libya.

Climate crises have already uprooted millions within the United States. In 2018, 1.2 million were displaced by extreme conditions, fire, storms, and flooding. By 2020, the annual toll rose to 1.7 million people. Most recently, the Maui fires, and the redevelopment and gentrification that may follow, have pressured many Native Hawaiians to migrate to the U.S. mainland. Native Hawaiians are a group that have been historically marginalized, and which includes many of the state’s poorest.

Although climate migrants have some basic rights under existing international human rights laws, many important protections that are provided to other groups, such as political refugees, are wanting. Currently, governments are responsible for any internal climate migrants, i.e. migrants who move within a country, but are not obligated to protect those crossing borders. “Refugee” is a term defined by the 1951 Refugee Convention and was initially created to manage populations fleeing violence or persecution in Europe during World War II. Excluded from the 1951 Convention are those fleeing from climate extremes or other natural disasters. As such, nations have limited plans to address climate migrants. Identifying who can be classified as a climate refugee is also not easy, as worsening weather conditions exacerbate poverty, crime, and political instability, as well as fuel tensions over diminishing resources.

Only within the last decade have major international organizations, such as the World Bank, recognized the relationship between climate change, migration, and sociopolitical instability. Recently, documents (e.g. NY Declaration for Refugees and Migrants, Global Compact for Safe, Orderly, and Regular Migration) have been published recognizing climate change as a driver of migration. In 2020, the UN Human Rights Committee ruled that climate refugees cannot be sent home if this would put their life in danger due to climate change effects. However, this ruling is not internationally binding, and special legal protection is still not offered for those affected worldwide by the international community.

Globally today, 50 million climate-displaced people outnumber those fleeing political persecution. The UN International Organization for Migration has estimated that there will be as many as 1.2 billion by 2050.

The act of migration is incredibly difficult for those who undertake it. Leaving behind home and community requires funds, contacts, and immense amount of courage. Migrants may find it challenging to find housing, childcare, and other public facilities in urban areas, or else may find themselves in employment with inhumane working conditions. The significant resources required for migration also means that the most vulnerable groups – those with low levels of income and education – are more likely to be left exposed to the continued impacts of climate change and thus, fall deeper and deeper into poverty. Many people who are in danger refuse to migrate – residents of small Pacific Island states resist the push from governments and organizations to move as sea levels rise, deciding instead to stay where they were raised and where their ancestors are buried despite growing risks to their safety and livelihoods.

Women are especially vulnerable to climate change impacts, due to gender roles and responsibilities, coupled with deep economic and social gender inequalities and underrepresentation in decision-making. During an extreme climate event, low-income women are 14 times more likely to die than men, due to higher responsibilities at home, little decision-making power within the family, or lack of education. Whether women migrate or remain where they are, they continue to be disproportionately impacted by climate change. In low-income countries, women are highly dependent on natural resources for their livelihood, and therefore face higher agricultural workloads and responsibilities, and are unlikely to seek help when disasters occur. When women opt to migrate, they are faced with higher risks of abuse, violence, discrimination and exploitation.

Climate change has and will continue to alter the land we live on and the lives we live. Migration can be a beneficial event for both the migratory and the receiving country: The Global North receives new groups of workers to replace the aging workforce. It is critical that sensible planning avoids focusing on worst-case scenarios, in which the developed world refuse migrants, and also refuse to help them at home. Instead, more resources can be put into mitigation efforts and disaster risk reduction. Migration is inevitable in our changing climate, and wealthy donor countries can use adaptation funding to support governments that are planning for climate mobility, both internal and cross-border. Finally, recognition of climate migrants as “refugees,” as defined by the United Nations, can provide the much-needed humanitarian statuses to the displaced.

Alicia Zhang

Research Assistant

This is a part of the AEC Blog series

The Environmental Movement Has a Long, Exclusionary History

A diagram highlighting the intersectional impacts of climate change. Source: Yale Sustainability

There is a long history of minorities being excluded from the environmental movement – from prohibition from outdoor spaces to being left out of environmental decision-making. A clean, healthy, and sustainable environment are human rights for all, and this long-standing exclusion has negative ramifications on how fairly ‘green’ transitions occurs.

Starting in the 1890s, the environmental movement emerged from the progressive era’s conservation movement. Leading naturalists and advocates, such as Henry David Thoreau and John Muir, encouraged wealthy, elite white males to revere nature and embrace outdoor pursuits. The environmental movement focused on preservationist issues by romanticizing outdoor spaces and conceptualizing the “environment” as wild or pristine spaces for recreational activities.

Around the same period, and expanding in the 1900s, concerns about unfair and hazardous working and housing conditions led rise to the labor movement and urban environmentalism. Urban green spaces became a focal point of environmental and political activism. While wilderness-oriented activist separated environmentalism from the working class and urban residents, urban park designers worked alongside the poor and built spaces where the middle-class and working poor interacted.

Urban and rural concerns were solidly linked in the 1960s, with the immense popularity of Rachel Carson’s Silent Spring (1962), which exposed the negative ramifications of toxic chemicals. Her book advocated for the right to a safe environment with a focus on home and community, along with nature and wild spaces. In response, middle class whites moved to more pristine and less toxic areas, while using their power and legal challenges to control the integrity of their communities. Meanwhile, minority communities became the dumping grounds for unwanted, toxic land uses, such as hazardous waste sites. Research soon made it clear the connection between race, class, and the environment. Environmentalism became immersed in the mass social movements of the 1960s, such as the civil rights and antiwar movements, giving rise to the environmental justice movement.

In the 1980s, environmental organizations grew increasingly large and mainly challenged environmental issues through legal and policy channels. Instead of grassroot activism, these organizations began to lobby Congress and business, and built close ties to industries. As these organizations grew and expanded, however, they became bureaucratized, hierarchical, and distant from local concerns. Wildlife and wilderness protection still dominated the agenda, and white males dominated the top leadership positions.

Today, environmentalism increasingly recognizes that systems of power and oppression have implications on climate change vulnerabilities, such as food access or energy affordability. However, those involved with the environmental movement are still mostly white, despite the disproportionate environmental impacts on minority and low-income communities and public opinion polls that have demonstrated the higher levels of environmental concern among minorities compared to whites.

The lack of diversity in environmental organizations is an unsettling facet of the largely exclusionary nature of many organizations, who have historically left minority communities out of the conversation. In 1972, the Sierra Club polled its members regarding whether the Club should “concern itself with the conservation problems of such special groups as the urban poor and ethnic minorities.” Forty percent of the respondents were strongly opposed to this, whereas only 15 percent were supportive. Attention to diversity matters has increased since then, but “diversity” gains have been from increased representation of white women.

Many avenues have the potential to increase minority participation in the environmental movement. In the forefront is the active inclusion of representatives from minority and low-income communities in the decision-making, design, and implementation processes of all environmental actions, from the grassroots level to the federal policy level. Many environmental organizations have active policies and practices that do not support inclusive cultures, but are working on developing transparent promotion processes, mentoring, and training programs in cultural competency which can help address the diversity problem.

Environmental history has largely excluded minorities and low-income communities, which impacts the way in which the environment is conceptualized. Access to a healthy living environment and to the outdoors are human rights, and the rapid onset of climate change impacts should add pressure to transition to a greener and more just world. Environmentalists need to ask what structural issues are preventing certain communities from being a part of this transition to put an end to a long history of environmental exclusion.

Alicia Zhang

Research Assistant

This is a part of the AEC Blog series

Non-Energy Benefits of Energy Programs

*Midwest Energy Efficiency Alliance. n.d. Non-Energy Benefits of Energy Efficiency.* *Available at:* *https://www.mwalliance.org/sites/default/files/media/NEBs-Factsheet_0.pdf*

Energy-related program assessments take account of the “non-energy benefits” (NEBs) that place a value on the many and diverse benefits for participants in energy efficiency programs beyond energy savings. Three-quarters of energy efficiency project benefits can come from NEBs including reduced energy burden for low-income residents, improved health and wellbeing, and a reduction in societal costs from air pollutants from fossil-fuel burning.

Regulators and utilities assess the cost-effectiveness of their energy efficiency programs by comparing the benefits of the program to the cost of delivering those programs. Forty states, including Texas, Florida, Ohio, and Pennsylvania, use cost-benefit tests that do not incorporate NEBs. The remaining 18 continental U.S. states that do incorporate NEBs, such as California, Massachusetts, and Washington, face challenges in quantifying NEBs. One difficulty is determining whether benefits are specific to the energy efficiency program itself, or whether they are caused by a different activity. For example, asthma incidences may be reduced by the reduction in energy derived from pollutant-emitting fossil fuels such as coal. But other initiatives, such as reducing exposure to tobacco smoke or mold, can also contribute to this reduction in asthma prevalence but which then cannot count as a NEB.

Further, reported monetization values for individual NEBs vary, due to different methods and assumptions used as well as differences in households, climate, and programs. Values may differ based on whether NEBs are included in a cost-benefit analysis:

As an adder, which is a dollar or percentage value added to energy benefits;
Using quantification, or the inclusion of money values for NEBs that can be quantified, such as a reduction in ratepayer costs; or
As a hybrid of both an adder and quantification, where an adder represents certain NEBs and quantification is used for others.

Regardless of the method used, accounting for NEBs in state policy and utility planning allows for the full potential and opportunities of energy efficiency programs to be captured.

Alicia Zhang

Research Assistant

This is a part of the AEC Blog series

Scope 3 Accounting is Difficult, But Necessary

The U.S. Environmental Protection Program (EPA) breaks carbon emissions into three different “scopes”: direct use of fuels (Scope 1), fuel use for generating electricity (Scope 2), and more indirect upstream and downstream emissions (Scope 3). Scope 3 emissions result from activities that are not done by the reporting organization but may be done by its suppliers or vendors, such as emissions from employees commuting or emissions from purchased goods or services.

Source: World Resources Institute and World Business Council for Sustainable Development. 2011. *Corporate Value Chain (Scope 3) Accounting and Reporting Standard.* Available at: https://ghgprotocol.org/sites/default/files/standards/Corporate-Value-Chain-Accounting-Reporing-Standard_041613_2.pdf

For most companies, Scope 3 accounts for more than 70 percent of their carbon footprint and therefore represents a large opportunity to reduce its overall emissions. Estimating the scale of Scope 3 emissions, however, is difficult, time-consuming, and resource intensive. These challenges often lead to poor or nonexistent reporting, partially [ES1] because businesses typically require data from many different suppliers to calculate their Scope 3 emissions. In lieu of robust and complete data, Scope 3 emissions can be estimated using computer models, although the results may not be detailed enough to provide good company-specific results. The complexities of Scope 3 reporting may have to be resolved soon, as there is increasing pressure from regulatory agencies such as the International Sustainability Standards Board (ISSB) and the U.S. Securities and Exchange Commission (SEC) to require Scope 3 disclosures.

Alicia Zhang

Research Assistant

This is a part of the AEC Blog series