Crumbling cliffs at Warwick’s Grand Atlantic development can’t be blamed solely on the Casuarina trees that grow there, according to tree expert Martin Brown.Mr Brown was speaking after developer Gilbert Lopes said that Casuarinas, which flourish along the exposed shoreline at the site, undermine the soft rock — and that it was the Bermuda Housing Corporation’s responsibility to keep the trees from returning to the cliffs.The Ministry of Community and Cultural Development declined to comment on the matter.Pictures of the Grand Atlantic cliffs have circulated online showing the latest collapse east of the development, reigniting the debate over safety issues at the controversial housing complex.Mr Brown said Casuarinas, an invasive species planted in the wake of Bermuda’s cedar blight, had proven a pest.But a host of other factors contribute to the undermining of weak rocks, Mr Brown added.“You can’t just blame it on the Casuarinas,” he said.“Most vegetation will cause damage if the rock is soft enough, and the substrate is soft enough for the roots to follow a path of least resistance — particularly exposed rock faces,” Mr Brown said.“But the fact of the matter is, in that specific case, given how soft the rock is there, even rain will erode it.“Given the nature of that cliff, whether it’s Casuarinas, Pittosporum or Hibiscus, roots will go through it. Any disturbance will cause falls.”The landscaper said: “They were introduced to reforest Bermuda and they were very successful ­— some would argue they’re too successful.“They’re naturalised and aggressive. They grow in coastal areas and you see them growing pretty well in nothing but salt water and craggy rock.”A qualified tree surgeon, Mr Brown said Casuarinas have also proven tough to get rid of.“For every one, they produce God knows how many seeds,” he added.Environmentalist and former Government Conservation Officer David Wingate has said Bermuda could benefit from a crew devoted to removing Casuarinas from the Island’s coastlines.Although the trees were popular 50 to 60 years ago, Dr Wingate wrote for this newspaper in 2003, Casuarinas had threatened to become “dominant on the coastline, including even our beaches”.Dr Wingate added: “Unlike the native coastal flora which grows prostrate and doesn’t obscure the vistas of the sea, the Casuarina continues to grow tall and straight even in this environment.“Where they are rooted in soft rock, the levering effect of strong winds causes them to break off large sections of cliff, thus hastening coastal erosion.”