In my home, the Beaver Lake Cree Nation, treaty six territory in Alberta, Canada, I am part of a community of 900 Woodland Cree people who have walked the land for thousands of years.

Under the land we call home sits the Alberta tar sands, the largest known reservoir of crude bitumen oil in the world – an area larger than England. Most of our land has now been leased out to the oil industry without the Canadian and provincial government following due process in their duty to consult the local people.

Beaver Lake is at a tipping point. Industry has moved in, but it has not yet destroyed everything worth saving and it is not too late to intervene.

Indigenous rights are the last stronghold we have to stop the unmitigated expansion of the tar sands at source

In 2013 a series of oil spills occurred in the region. One spill was discovered under a lake on the south-west shore, where elders say our ancestors are buried. Over 200 animals and amphibians died as a result and over 300,000 kg of oily vegetation was removed from site. How do I explain to my children what is going on? What do I say when my little girl asks: “Why is the water poisoned?”

Facebook Twitter Pinterest ‘We used to be surrounded by water. There was swamp and the rest was lake. Now there’s no water.’ Video by Niki Young and Sean Devlin

In May 2008 the Beaver Lake Cree filed a lawsuit, taking the governments in Canada and Alberta to court. The case rests on a treaty entered in 1876 under which the Beaver Lake Cree agreed to share parcels of huge areas of land, in return for a guarantee that “as long as the sun shines, the grass grows and the rivers flow we can continue our traditional way of life”, including “traditional rights to hunt, fish, trap and gather for food and support”. However the treaty says exclusions may be made for land “required or taken up for settlement, mining, lumbering or other purposes”. Canada is founded on treaty six; it is our direct connection to the British Crown and acknowledges my people and our relationship with the land.

In April 2013 the Alberta Court of Appeal ruled in favour of the Beaver Lake Cree. We are the first community to ever be granted a trial in relation to the cumulative impacts this industry has had on our inherent Treaty rights to hunt, fish, trap and gather plant medicine.

Indigenous rights are the last stronghold we have to stop the unmitigated expansion of the tar sands at source. The Beaver Lake Cree are carrying a case on their backs that could set historical precedence: success would mean that it would become much harder if not impossible to expand tar sands projects and would greatly curtail the industry’s expansion plans.

Currently, we are preparing for trial by gathering oral testimony from community members, hiring scientists and historians to complete the required cumulative impact reports, and gathering the documentary and expert evidence necessary for trial.

This is no longer an “Indian” problem. If you breathe air and drink water, this is about you too. The battle is to protect one of the world’s most important carbon sinks – the boreal forest – and to stop the expansion of Canada’s largest industrial producer of greenhouse gases. It is about the inherent rights of First Nations people, collective basic human rights and the rights of nature.

Our story is an example of solidarity at its finest. As it has grown, so has our list of allies. Solidarity has meant that the Beaver Lake Cree have been able to create a means of resistance while offering a solution. Alongside support from groups in the grassroots climate movement, we have benefitted from an international campaign started by the Co-operative Group and the World Wildlife Fund (WWF). It has fundraised over £250,000 for our case, which they described as “perhaps our best chance of stopping or dramatically curtailing tar sands expansion and the global climate disaster it threatens”.

We are seeing this movement already having an impact on the fossil fuel industry, with a major Shell project shelved following high costs, oil price volatility, and First Nation opposition.

We believe the case is winnable and presents a very high risk of stranded assets. Any investor claiming to be responsible should look elsewhere to create healthy and sustainable investments that do not threaten future generations.

Will divestment from these companies change everything? No, but combined with such things as indigenous rights practices we will make a difference. Will it define solidarity between frontline impacted communities, the climate change movement and responsible investors? Yes.

It’s inspiring to see the Guardian joining this audacious movement and to know that people are drawing connections between their investments and the industries that are devastating our communities in Canada and pushing us globally towards catastrophic climate change.