Are your seasonal allergies caused by botanical sexism? The answer is muddy

Debates are flourishing over whether the growing number of people who live with seasonal allergies is because of a sexist decision by city planners.

According to researchers, more than a quarter of Canadians suffer from seasonal allergies.

Some blame botanical sexism -- a term that describes a city's preference to plant male trees because they do not cover the ground with fruit or flowers.

However, male trees boast a high pollen production, which, if planted in abundance, could mean that people with allergies are suffering more than necessary.

"Some specialists say it's better to plant male trees in cities because they don't produce fruit," said Sarah Tardif, a PhD student in biology at Université du Québec à Montréal (UQAM). "We don't know if it's true or not."

Tardif is a member of UQAM's urban forest research chair, which aims to "investigate how trees are distributed in the world, how their diversity affects the functioning of forests, how they interact with each other, with other organisms, as well as with us."

Part of her research is taking inventory of all the trees on the Island of Montreal.

"We know that some species may be more allergenic than others," explains Tardif. "For example, all the species pollinated by the wind are more allergenic than the species pollinated by insects."

She notes that though birch trees are far from the most abundant species in Montreal, they produce a large quantity of pollen that can travel farther than other types of trees.

"It's one of the trees that grow very fast at the beginning of the development, so we call them the pioneer species," said Tardif on why cities continue to plant them. "If you want a big tree in a few years, it's good, but for allergies, it's not the best one."

Regardless, she says allergies aren't generally factored in when planting trees in cities.

"We don't have a lot of information about what pollen we have in the air, and especially what species are more allergenic compared to the others," she said, explaining that's one of the goals of her PhD project. "The main objective of my project is to see what type of pollen we have in the air."

One of the questions she wants to answer is if the pollen caught in her traps is from trees nearby or far away.

"We link the pollen data with allergic symptoms from the population nearby our traps," Tardif said.

The researcher, who lived with seasonal allergies in her native France, says she doesn't have the same afflictions in Montreal.

"We need more knowledge about what is the allergenicity of the trees because the allergenicity of the trees comes from different things," said Tardif. "It can be the the quantity of pollen that is produced by the trees, but also [what is] released."

She adds that meteorological factors can also play a role.

"When there is more wind or more dry weather, and also before thunderstorms," Tardif lists. "It shows that there is more pollen released in the air at this point."

For its part, the City of Montreal says it doesn't know the proportion of male-to-female trees on its territory.

"We don't take tree sex into account in our planting choices, except for species that produce fruit, which may require more maintenance," said Camille Bégin, a public relations officer with the City of Montreal.

Officials maintain that the primary issue is whether the pollen produced by certain types of trees is allergenic -- regardless of whether the tree is male, female or has both male and female flowers.

"New studies point the finger at certain species of maple, which are said to have significant allergenic potential, and are found in large quantities in several major cities, including Montreal," said Bégin.

She adds the City of Montreal is working with the UQAM lab, headed by Dr. Alain Paquette, to learn more about the subject.

"The results of this research will certainly guide future plantings," said Bégin.

In short, there is still much left to be discovered when it comes to the relationship between different types of trees and the increasing number of people who have allergies.

"Maybe some of them [the trees] are here by regeneration or just seedlings from other trees, but most of them are planted, so we can control what we plant," said Tardif. "This is the specificity of the cities. Knowing that, we can select the best trees according to allergy, and also the ecosystem services we want for the population."

All the main allergenic tree species in Quebec are listed here.