They’re not elided in your examples. There are no hard and fast rules about elision. You can always check in your dictionary to see what the phonetic spelling is for any individual word. If you looked up “environment”, for example, you’d see that the “n” is present. Same for “recognise”: you’d see that the “g” is present.
There’s always a phonetics chart at the beginning of dictionaries. Most of the time, the consonants look the same as they do in the alphabet so it isn’t difficult to check if a consonant is pronounced or not.
However, there’s sometimes a difference between the way a word sounds in isolation and the way it is pronounced in connected speech. For example, “What are you going to do?” could be pronounced like this in connected speech: “Whadya gonna do?”
If you’d like to know a bit more about pronunciation changes in connected speech, you could look at the following site: http://www.jalt.org/pansig/2006/HTML/Brown.htm