A new report says urban forests in the Greater Toronto Area are increasingly stressed and governments must invest in "living, green infrastructure" to protect this greenery.

The report, "State of the Urban Forest in the Greater Toronto Area," says that development, climate change, invasive pests and violent storms are wreaking havoc on urban forests in the Toronto area. The coalition is an alliance of organizations concerned about Ontario's forests.

"We are seeing increasing stresses on the urban forests," Janet McKay, chair of the Green Infrastructure Ontario Coalition, told Metro Morning on Thursday.

"It can't be fixed by just planting. We have to protect what we have. We can't plant our way out of this."

McKay said if governments do not invest in trees, the impact will be felt over time.

"Our quality of life will definitely go down. Our health will be affected. Our daily lives will be affected. Studies have shown that urban forests and green space improve our mental health, not just our physical health."

Residents are calling on city councillor Jaye Robinson to protect the trees of the Lawrence Park neighbourhood in Toronto on May 21, 2016. (CBC)

The report says only four species, maple, cedar, ash and buckthorn, make up 54 per cent of the tree population in the GTA, which means the urban forest is vulnerable to pests and disease. Violent storms, such as the ice storm of December 2013, have caused tree loss in many municipalities. Development is also removing soil volume, which means growing space is restricted.

"Urban development practices often remove nutrient-rich top soil and restrict or redirect the flow of water. These changes put newly planted and well established trees at risk because they may be deprived of the water and nutrients needed to survive," it reads.

"Trees that line city streets often have very little room in which to expand their roots and branches. Restricted space together with poor soil quality creates an inhospitable environment for trees."

The report says the emerald ash borer, an "invasive wood-boring beetle," is a good example of a pest that is damaging and destroying Toronto area trees. Millions of ash trees are at risk. The report calls for increasing the diversity of trees in the region to ensure the survival of a greater number of trees.

McKay said urban forests are a valuable resource and should be seen as assets. She said governments should spend on urban forests in the same way they spend on roads and bridges because of the benefits that trees provide.

"What we see is that the urban forest is really vital living, green infrastructure, providing us incredible benefits," she said.

The ice storm of December 2013 left many trees in Toronto broken and bent. Violent storms are seen as one reason why the urban forests in the area are stressed. (Matthew Sherwood/Canadian Press)

These benefits include improving air quality, which the report says is worth $36.5 million annually, and saving energy through shade and cooling, which it estimates is worth $20 million annually.

"Those are benefits that really can't be replaced by grey infrastructure. We really need to be thinking about how we are going to protect this resource so it keeps giving us these benefits."

The report was a collaborative effort involving urban forest studies from 17 municipal and regional governments.

"It's the first time we've had the big picture," she said.

The report says most municipalities do not have adequate resources to manage their forests, there should be comprehensive approach to protecting this asset, more study is needed, and infrastructure spending should including spending on green infrastructure.

It identifies four priorities to protect urban forests: