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ICLEI Regional Executive Committee

ICLEI’s North American Regional Executive Committee, also known as RexCom, is a powerful force for sustainability action for the U.S. and Canada. Comprised of local elected officials from the ICLEI network, RexCom is responsible for guiding our local governments in their response to the pressing biodiversity, pollution, and climate crises.


Every three years, parallel regional elections take place in all 9 ICLEI regions to elect the ICLEI Global and Regional Executive Committees. Representatives from eligible ICLEI Members can apply in their region by submitting an application, and all eligible ICLEI Members then vote, which is then followed by the ICLEI Global Executive Committee elections.

Meet the ICLEI U.S. Regional Executive Committee


Niki Armacost

Mayor of Hastings-on-Hudson, New York, USA

I have served as Mayor of Hastings-on-Hudson, NY since 2019, and before that as Trustee since 2009. Under my leadership, Hastings is currently the highest-ranking Climate Smart Community (CSC) in New York State. We have adopted the New York Stretch Energy Code, signed up for Community Choice Aggregation (CCA), expanded financing for energy efficiency, passed a Low-Embodied Carbon Concrete Resolution, invested in electric vehicles, alternative fuel infrastructure and resiliency planning, implemented a complete streets policy, promoted “buy local” initiatives, supported volunteer-run community repair and reuse programs, dedicated over 89% of municipal-owned open space as parkland, commissioned studies that assess our climate vulnerabilities, created a Mayor’s Climate Youth Council, and adopted a Climate Emergency Declaration.

I am a proud ICLEI-USA Race to Zero Leader. Other roles include serving on the Executive Committee of the Westchester Municipal Officials Association (WMOA) where I Co-Chair the Sustainability and Housing Sub-Committees.

I am also a member of the Environment, Energy and Technology Policy Committee and the Women’s Advisory Committee of the New York Conference of Mayors (NYCOM). I have used my platform as Mayor to champion sustainability initiatives, not just in my own municipality but also among neighboring municipalities, as well as in the region, nationally and internationally.

I believe that climate change is the single most important issue we face as a global community and the burden of addressing it falls most heavily on local governments. By sharing knowledge, innovative ideas and best practices we can support one another in making a demonstrable difference. ICLEI embodies this ethos, and I pledge to do my utmost to support its efforts.

Jeni Arndt

Mayor of Fort Collins, Colorado, USA

I have the pleasure of being the mayor of the town where I grew up – Fort Collins, Colorado. Fort Collins is an international leader for how to make sustainability work at the local level. If chosen to serve on the Regional Executive Committee for North America I will bring Colorado pragmatism and a global perspective to help advance the vision of ICLEI member communities.

I believe deeply in the importance of education for all, having earned degrees in Sociology, Geography, and Special Education, as well as a PhD in Literacy & Language. I developed an international lens throughout my career, including as a Peace Corps volunteer in Morocco (1990-92) and living and working in education in Mozambique (2002-08). These experiences enhanced my commitment to shared global sustainability leadership.

Before being elected Mayor in 2021, I served four terms as a Colorado State Representative beginning in 2015, focusing on climate-related issues such as water and agriculture. At the local level, strong community support in Fort Collins has led us to set leading-edge targets that drive policy and investment in a sustainable future. Recently, our City Council adopted an additional greenhouse gas reduction target on our way to carbon neutrality.

A few highlights of my time as Mayor include: recognized by the Climate Reality Project with a leadership award; presented at the ICLEI World Congress in Malmo, Sweden; presented at ICLEI’s Zero Carbon Cities Forum in Tokyo, Japan; and gave two presentations at the U.S. State Department’s Cities Summit of the Americas in Denver, Colorado.

As a committed leader for sustainability I have a proven record of bridging divides to help communities implement practical solutions. I’d be honored to serve as a member of ICLEI’s RexCom for North America.

Barbara Buffaloe

Mayor of Columbia, Missouri, USA

Barbara Buffaloe is the Mayor of Columbia, MO, the fourth largest city in Missouri. She serves on the Board of Directors for the Missouri Innovation Center, and as an ex-officio member on the Board of Directors for REDI and the Columbia Chamber of Commerce.


Mayor Buffaloe is Chair of the Environment Committee of the US Conference of Mayors and will be part of a delegation representing US Mayors at COP28 in December 2023. Mayor Buffaloe is part of the 7th cohort of Mayors for the Bloomberg Harvard Civic Leadership program.


Before being elected Mayor of Columbia, she served as Columbia’s first Sustainability Manager. Mayor Buffaloe coordinated the development of Columbia’s Climate Action & Adaptation Plan that lays out a vision and strategies to address risks posed by climate change and contributes to international efforts to reduce greenhouse gas emissions. She has presented on the topics of climate action at numerous conferences, including the US Department of Energy’s Better Buildings Summit, the Midwest Climate Collective’s Climate Summit, and the Advancing Renewables in the Midwest conference.


Mayor Buffaloe serves as advisor to the Board of Directors for the Urban Sustainability Directors Network (USDN) and is past Board Secretary. Mayor Buffaloe co-founded the Heartland Local Government Sustainability Network, a network of City and County sustainability managers and directors from seven Midwestern states whose charge it is to create additional momentum for promoting sustainability throughout the Heartland. She believes in the power of regional collaboration and knows that ICLEI’s network of communities can make a difference by partnering on projects and programs together.