I have not seen such research in regards to human sexual development that reached a consensus that sexual orientation is an environmental phenomenon.
No one, including me, is saying that sexual orientation is an environmental phenomenon. I am saying, in concordance with the preponderance of scientific evidence, that sexual orientation is a multi-factorial phenomenon that includes environmental effects.
what research states a consensus you are talking about.
APA(link previously given): "There is no consensus among scientists about the exact reasons that an individual develops a heterosexual, bisexual, gay or lesbian orientation. Although much research has examined the possible genetic, hormonal, developmental, social and cultural influences on sexual orientation, no findings have emerged that permit scientists to conclude that sexual orientation is determined by any particular factor or factors."
Here is a textbook on psychiatry,
Principles of Psychiatric Nursing:
Principles and Practice of Psychiatric Nursing - E-Book
"No conclusive evidence supports any one specific cause of homosexuality; however, most researchers agree that biological and social factors influence the development of sexual orientation"
Here's five articles of the sort that such declarations rely upon.
Långström, Niklas; Qazi Rahman; Eva Carlström; Paul Lichtenstein. "Genetic and Environmental Effects on Same-sex Sexual Behaviour: A Population Study of Twins in Sweden".
Archives of Sexual Behavior. Archives of Sexual Behavior.
39 (1): 75–80.
Schumm, Walter R.
"CHILDREN OF HOMOSEXUALS MORE APT TO BE HOMOSEXUALS? A REPLY TO MORRISON AND TO CAMERON BASED ON AN EXAMINATION OF MULTIPLE SOURCES OF DATA".
Journal of Biosocial Science.
42 (06): 721–42
Kendler KS, Thornton LM, Gilman SE, Kessler RC.
"Sexual orientation in a U.S. national sample of twin and nontwin sibling pairs". Am J Psychiatry. 157 (11): 1843–6.
Lung, F.W.; Shu, B.C.. "Father-son attachment and sexual partner orientation in Taiwan". Comprehensive Psychiatry. 48 (1): 20–6.
Bailey: J Pers Soc Psychol, Volume 78(3).March 2000.524–536