It's actually applied science with an emphasis in environmental biology, apparently. I can't actually find the year it was given to him, nor can I find any evidence of him using the diploma for any actual scientific use during the interim where he apparently taught science for several years using his second degree in education from the University of Queensland. He joined the creationist movement in 1979 and was born in 1951, leaving only six years after a four year degree that he spent as a teacher.
So I wouldn't say he really has a background in it when he's never worked in the field, but I don't consider teaching high school science to be in the field, so that's at your discretion if you consider it both science and teaching or just teaching.
Of course, this is just splitting hairs, but I still think it's a little gratuitous to say he's had a background in science.