▁streams ▁increases ▁run off , ▁reducing ▁the ▁quality ▁of ▁the ▁water ▁and ▁causing ▁harm ▁to ▁the ▁e cos ystem ▁of ▁the ▁water way . ▁Hor se ▁ex crement ▁tends ▁to ▁f oul ▁these ▁water ways , ▁as ▁does ▁the ▁accum ulation ▁of ▁car c ass es ▁that ▁result ▁when ▁fer al ▁horses ▁per ish , ▁adding ▁to ▁the ▁negative ▁environmental ▁impact ▁of ▁this ▁ex otic ▁species ▁in ▁Australia . ▁ ▁Al pine ▁areas , ▁such ▁as ▁those ▁of ▁Kos ci usz ko ▁National ▁Park , ▁are ▁at ▁particular ▁risk ; ▁low - g row ing ▁al pine ▁fl ora ▁is ▁highly ▁vulner able ▁to ▁tram pling , ▁and ▁the ▁short ▁sum mers ▁mean ▁little ▁time ▁for ▁plants ▁to ▁grow ▁and ▁recover ▁from ▁damage . ▁The ▁b iod iversity ▁there ▁is ▁high , ▁with ▁ 8 5 3 ▁species ▁of ▁plant , ▁ 2 1 ▁of ▁which ▁are ▁found ▁now here ▁else . ▁E ros ion ▁in ▁the ▁lim estone ▁kar st ▁areas ▁leads ▁to ▁run off ▁and ▁sil ting . ▁S ph ag num ▁m oss ▁is ▁an ▁important ▁component ▁of ▁high land ▁b ogs , ▁and ▁is ▁tr ample d ▁by ▁horses ▁seeking ▁water . ▁ ▁Fer al ▁horses ▁may ▁also ▁reduce ▁the ▁rich ness ▁of ▁plant ▁species . ▁Ex pos ure ▁of ▁soil ▁caused ▁by ▁tram pling ▁and ▁veget ation ▁removal ▁via ▁gra zing , ▁combined ▁with ▁increased ▁nut ri ents ▁being ▁rec yc led ▁by ▁horse ▁d ung , ▁favour ▁we ed ▁species , ▁which ▁then ▁in va de ▁the