SUDBURY -- Monarch butterflies are a beautiful sight, but the species is declining.

In Sudbury, the mining company Vale is planting and growing milkweed, an essential plant for the survival of monarchs, in an effort to boost the population.

"Monarch butterfly populations globally, are stressed, primarily due to habitat loss and we understand this and we felt like there was an opportunity for us to potentially give back and help this population," said Quentin Smith a Vale Project Engineer.

Once barren, now regreened slag piles flourishing with milkweed are attracting monarch butterflies to the area and helping the species survive.

Vale has been growing and planting milkweed for the past decade.

A crucial plant for the survival of monarchs and the only food source early in their lives.

"The monarch butterflies are very unique in that in the larval stage, at the caterpillar stage they will only eat milkweed. And so because of this fact, if milkweed is not present in an area, the monarchs will migrate around these areas and look for areas where milkweed is present," said Quentin Smith.

Jennifer Babin-Fenske is the coordinator for Earth Care Sudbury for the city and says the eco-friendly milkweed and monarch project is a great one for a number of reasons.

"Not only is it helping monarchs and their global plight and struggles with their lack of habitat and loss of habitat, but it's helping with our local biodiversity, which helps our ecosystem become more resilient to climate change," said Jennifer Babin-Fenske of the City of Greater Sudbury.

Vale says it's trying to provide an important contribution to the environment surrounding the Sudbury basin.

"Monarch butterflies are important pollinators and if we can encourage their return to this area we will get those pollinators that are coming back and helping the ecosystem in that way," said Quentin Smith.

Vale grows up to 500 milkweed plants every year. Some are donated to schools to establish butterfly gardens and the rest are planted on site in areas that are visible to the community.