The process towards respect towards and inclusion of local populations in the decision-making processes on environmental matters has taken another major leap forward: Guyana has ratified the Regional Agreement on Access to Information, Public Participation and Justice in Environmental Matters in Latin America and the Caribbean (Escazú Agreement; text of the Agreement in English here).
The Escazú Agreement is the only legally-binding agreement that emerged from the Rio +20 meeting in 2012 and aims at implementing Principle 10 of the Rio Declaration:
Environmental issues are best handled with participation of all concerned citizens, at the relevant level. At the national level, each individual shall have appropriate access to information concerning the environment that is held by public authorities, including information on hazardous materials and activities in their communities, and the opportunity to participate in decision-making processes. States shall facilitate and encourage public awareness and participation by making information widely available. Effective access to judicial and administrative proceedings, including redress and remedy, shall be provided.

The agreement was adopted on 4 March 2018 in Escazú, Costa Rica, and was opened for signature on 27 September 2018 at the UN Headquarters in New York.
Thus far it has been signed by 16 countries and enters into force upon ratification of 11. With Guyana being the first state to ratify this agreement, the first step towards entering into force is taken. The Escazú Agreement mirrors the provisions (and the title) of the 1998 UNECE Aarhus Convention and thus rests on three pillars: access to information; public participation; and environmental justice. But beyond that, the Escazú Agreement establishes means for capacity-building and cooperation, as well as a clearing house mechanism that is to be overseen by the Economic Commission for Latin America and the Caribbean.
A significant advancement compared to the Aarhus Convention is the fact that Article 9 of the Escazú Agreement establishes state obligations for the protection of human rights defenders in environmental matters. This means that upon entry into force of the agreement states are required to protect human rights defenders and prosecute those that threaten them.
While the Rio Declaration provides for the normative setting of the Escazú Agreement, the Aarhus Convention serves as a template that can be altered and expanded. In combination with the UN Declaration on the Rights of Peasants and Other People Working in Rural Areas (see my older blog post here), which the UN General Assembly adopted in December 2018, an increasing normative (maybe eventually customary) framework for the participation of local populations is developing in the United Nations.