Before 2009, the Yale School of Forestry and Environmental Studies never had more than one female professor at a time.

When Sir Peter Crane became the dean of FES in the summer of 2009, there were zero tenured women on the faculty. But over the last five years, FES has made strides in recruiting female professors, and four have joined the school as tenured faculty. In the 2014-’15 academic year, four of the 22 tenured faculty members at FES are women. Still, Crane said the school faces many more challenges on the path towards a gender-balanced faculty.

“That’s better than it was but it’s not as good as it need to be,” Crane said. “We’ve still got a long way to go, both in terms of the male-female representation and just as importantly in terms of diversity more broadly.”

According to the American Association for University Women, women’s participation in doctoral programs, and the number of women faculty on college campuses, has grown. Women make up 27 percent of tenured faculty at colleges and universities that grant four-year degrees. At FES, 18 percent of tenured faculty are women.

FES faculty members interviewed suggested that the two-body problem — when two partners do not both receive positions at the same university or region, forcing one of them to reject an otherwise desirable offer — was the major contributing factor for this gender imbalance.

Under Crane’s tenure, two additional women were recruited for tenure-track positions, but neither woman accepted the offer because her spouse — who also worked in academia — could not find employment at the University. Crane noted that this two-body problem is difficult to solve because it is a university-wide problem.

FES professor Kenneth Gillingham echoed Crane’s sentiments, adding that the gender balance among faculty is a continual challenge at Yale that requires collaboration among departments and schools.

According to a 2008 report from the Stanford University Clayman Institute for Gender Research, 70 percent of professors in American universities are in dual-career relationships, emphasizing that this trend is especially relevant for women scientists.

To tackle gender imbalance, Crane said, FES must focus on recruitment of a diverse set of top candidates. Crane added that he believes female representation in FES will increase over time.

“We want our school to reflect our society broadly,” he said. “We need to connect with a range of communities.”

Karen Seto, a tenured professor at FES, agreed that recruitment is a way to improve female representation in FES faculty, but added that the two-body problem must be specifically addressed as well.

For women in heterosexual relationships where their partner is older and established in their career, it is unlikely that he will move, Seto explained.

“A lot of women don’t even apply because moving is not an option,” Seto said.

Michelle Bell, a tenured professor at FES, said in an email that this problem might be exacerbated by Yale’s location in New Haven because employment opportunities are more likely to be limited than other universities in larger cities.

Seto added that policies to accommodate the two-body problem would be “revolutionary” and would dramatically improve the gender imbalance.

Avana Andrade FES ’15, co-leader of Yale Environmental Women (YEW), said that the issue of women’s underrepresentation is discussed among students.

The student-body gender ratio at FES is skewed towards women, but the opposite is true for FES faculty, Crane said.

The gender ratio of FES faculty does have an effect on students, Andrade said.

“It’s important to have female mentors and models that can clue you into their challenges,” she added.

The Yale School of Forestry was founded in 1900.