GRI Secretariat

Led by the Chief Executive and the Executive Team, the Secretariat implements GRI’s strategic work plan, in addition to managing network and institutional communications, global outreach, stakeholder relations, marketing and financial administration.

The GRI Secretariat is headquartered in Amsterdam, The Netherlands, where we have around 90 staff members based, while our work is supported by a network of seven Regional Hubs. 

GRI Executive Team

Chief Executive


Responsibility for overseeing GRI's strategic work program and organizational management.

A global search has been initiated to recruit a new chief executive, following the departure of Tim Mohin in October 2020. 

Bastian Buck
Chief of Standards


Responsibility for the ongoing maintenance, development, implementation and enhancement of GRI’s Sustainability Reporting Framework.

Bastian, who joined GRI in 2006, has in-depth institutional knowledge of GRI’s technical development and played a key role in the successful launch of GRI’s G4 Guidelines in 2013, following which he became Director Reporting in the Standard Department. Since then he led the introduction of the GRI Standards in 2016.

Bastian has presented on sustainability reporting in more than 30 countries and is highly experienced in international and multi-stakeholder expert working. He holds a Masters in Business Administration, focusing on sustainable development, from Erasmus University Rotterdam.

Mirjam Groten
Chief Business Development Officer


Responsible for delivery of reporting services and training, including the membership program – the GRI Community.

Mirjam joined GRI in 2019 to lead the organizations business development functions. She has a wealth of experience from commercially focused management roles in both the not-for-profit and private sector. She previously worked for Fairtrade, in Europe and then Australia and New Zealand, latterly as Business Development Director.

Earlier in her career, Mirjam worked within global brands in the FMCG sector. She holds a Bachelor of Science in Food Technology and a Bachelor of Commerce in Business Management. 

Ásthildur Hjaltadóttir
Chief Regional O


Responsible for content development and program delivery, and closely collaborates with GRI’s Regional Hubs worldwide.

Ásthildur joined GRI in 2007 and has held various positions in the organization, including project managing the development of the G4 Guidelines, and Director of the Report Services and Training and Coaching Departments. Since 2017, Ásthildur has been responsible for GRI´s regional offices and program implementation.

Before joining GRI, she worked in various roles for international organizations in Brussels, Belgium, and The Hague, Netherlands.

Marco van der Ree
Chief Development Officer


Responsible for directing and implementing GRI's funding and program partnership strategy with institutional, corporate and foundation donors.

Marco leads GRI’s fundraising strategy and oversees outreach to institutional, foundation and public donors. He joined GRI in 2019 and was previously Director Business Development and Fundraising for the European Institute of Innovation and Technology’s Climate Knowledge Innovation Community (EIT Climate-KIC).

Marco has more than 20 years’ experience with international organizations, in partnership building, fundraising, campaign delivery and program management. These include roles with the Collaborating Centre on Sustainable Consumption and Production, UN Volunteers, UN Office for Project Services, UN Capital Development Fund and UNDP. He holds a Masters in International Relations from the University of Amsterdam.

Peter Westra
Chief Operating Officer


Responsibility for day-to-day management of Secretariat operations.

Peter, who joined GRI in 2008, is responsible for Secretariat operations – covering planning, budgeting, reporting and controls, finance and legal, IT, HR, and quality and sustainability management.

During a career in the IT industry spanning more than 25 years, Peter held various senior financial and management positions, including Senior Vice President and COO of several international businesses. From 2004 - 2008, he ran his own consultancy firm, providing business and strategy advice to SMEs.

Peter Paul van de Wijs
Chief External Affairs Officer


Responsibility for GRI’s marketing and communications, public affairs and policy.

Peter Paul joined GRI in June 2018. He has responsibility for global advocacy, leading GRI’s internal and external communications strategy and maintaining the external relations.

With over 20 years experience in communications and sustainability roles, Peter Paul has held executive positions at the LEGO Foundation and the World Business Council for Sustainable Development. He holds a degree in Communications from the College for Economic and Business Administration Studies, Eindhoven.