Sr McCarron, who was 85, became known for her work on behalf of the Ogoni people in Nigeria whose lands were destroyed by oil production.
She became an international voice for Ogoni leader, Ken Saro-Wiwa, during his imprisonment and after his subsequent execution.
Later in Ireland, she supported communities in Mayo opposed to the running of a gas pipeline across the landscape during the turbulent ‘Shell to Sea’ campaign.
James Orr from Friends of the Earth with Fiona Joyce and Majella McCarron from the Stop the Drill campaign in 2016. Pic: Jonathan Porter/Presseye
She also backed the successful campaign against fracking in Co Leitrim and more recently threw her weight behind communities in northern Ireland challenging gold-mining plans for the Sperrin Mountains.
Sr McCarron was born in Derrylin, Co Fermanagh and joined the Our Lady of Apostles missionary order in the 1950s.
She studied science at University College Cork before being assigned to a parish in Nigeria where she spent 30 years teaching.
It was during her time there that she became aware of the plight of the people of Ogoniland, a region of mangroves, farmers and fishing families in the Niger delta.
Oil companies moved there in the 1950s, destroying farmland, fishing grounds, natural habitats and villages.
Local opposition was repressed by government and militia but the Movement for the Survival of Ogoni People (MOSOP) began to gain international attention under the leadership of writer and activist, Ken Saro-Wiwa.
Tensions reached a peak in the early 1990s and Mr Saro-Wiwa and eight other activists were arrested for alleged involvement in the murder of four Ogoni chiefs who had disagreed with him on strategy.
The allegations were condemned around the world as being without substance and the trial without proper procedures but all nine were hanged.
While on death row, Mr Saro-Wiwa wrote letters and poems which were smuggled out of prison to Sr McCarron.
The controversy over the executions led to oil companies abandoning operations in Ogoniland but the legacy of environmental damage continues.
The United Nations Environment Programme has been supporting the Nigerian government in attempting a clean-up.
The Love Leitrim group which formed to fight fracking in the county said: “We’ve lost an incredible campaigner and advocate for human rights.
“Sr Majella’s legacy will live on to inspire small communities standing against the might of corporate greed.”
Shell to Sea campaigner, Ruairi McKiernan, said Sr McCarron was a “powerful courageous voice who has left her mark”.
Maynooth University, to which Sr McCarron donated the writings Mr Saro-Wiwa sent her, expressed their appreciation for allowing the archive to be brought to the attention of the world.
The Our Lady of Apostles order said they were in mourning for a member who would be deeply missed.
Sr McCarron, who was one of a family of five siblings with two surviving brothers, spent her ‘retirement’ at the orders Ardfoyle Convent in Cork where she continued to campaign through letter writing.
She died at Marymount Hospice, Cork on Saturday and her funeral takes place at the Convent on Tuesday.
