A battle of the sexes is happening in Canada's urban forests and the losers are those with allergies.
A study shows the dominance of male trees is making it worse for people who suffer from allergies.
The study found that male tress produce more pollen than female trees. But because female trees tend to make more of a mess with flowers and fruit, cities and nurseries shy away from planting them.
Therefore male, pollen-producing trees usually exist.