Difficult question. The 18000 possible sites is an estimate only. 3000 have actually been identified. Sites this particular newt needs for breeding are deepish ponds with a decent amount of aquatic vegetation. These are being lost at a fair rate- filling in accounting for some and neglect accounting for the rest- silting up, becoming stagnant. Although Britain has a reasonable population of this newt compared to some European countries, the critria here is breeding sites- are they close enough to allow a decent gene pool, is the population actually large enough to be self-sustaining.