«The work of art has no place outside nature; its place is in nature,» says Nicolás Uriburu. Graduated in architecture, after starting a career as a landscape painter and wildlife portraits in the early 60s, the young Argentine artist of twenty-five years makes a journey that leads him in particular to Paris and New York. He discovered the environmental problem and became aware of the extent of the pollution that «will lose the world». The striking contrast between the wonderful South American landscapes he walked and the river separating Buenos Aires from its southern suburbs, strikes him forever. Carrying toxic heavy metals discharged by the chemical industries, Riachuelo, which bathes his hometown, is among the ten most polluted sites in the world.
It is necessary to commit, to protect Nature and to denounce its exploitation. The artist decides to leave the flat surface of his paintings and work in the urban space. Since he was a painter, Nicolás Uriburu decided to color the water, literally. He began research on the pigment to be implemented. The substance must not be polluting or toxic and it opts for fluorescein, a red powder that, in contact with water, becomes green and fluorescent. He made his first «colouring» in 1968, during the famous Biennale («Green Venice»); two years later, three other projects followed: New York (East River colouring), Paris (Seine colouring) and Buenos Aires (Rio de la Plata colouring). Painting nature, greening urban waterways in sites of great heritage value, without authorization, his four interventions alert the public authorities; his performances are followed by the intervention of law enforcement. Nicolás Uriburu knows interrogations and police stations! The press relays the events and gives him local and international visibility. The cause of the artist is growing. Nicolás Uriburu now wishes to spread his ecological convictions and, in 1973, theorizes them in a Portfolio-Manifesto: "I denounce with my art the antagonism between nature and civilization. (...) More advanced countries are destroying water, land, air.”

The artist, since 1971, also denounces the deforestation of cities and deforestation. He published an open letter in the daily La Nación, to protest against the slaughter of jacarandas in Chile’s square in Buenos Aires, highlighting the benefits of the presence of trees in urban areas, in terms of aesthetics, of connection of city dwellers with the rhythm of nature, public hygiene and freshness. “I demand an end to this killing of trees. (...) It is a total lack of cultivation to reduce them to cement.” A real movement of opinion is formed. The artistic gesture of Uriburu finds again an extension in the public life, and inaugurates, in parallel to the colorations, another series of actions: the plantations of trees, in particular in urban environment.
After dozens of color actions around the world in the late 1990s, Uriburu feels isolated. He will now collaborate with the association Greenpeace; this collaboration, unique in art history, illustrates the porosity between artistic gesture and militant action.
“Green water is the extra soul that nature gives to its nourishing element. It is therefore an act of love, at the elementary level, on which is based both the sensitivity of the look that the Argentine artist casts on the world and his own reflection on this look,” wrote Pierre Restany in 1974.