In a three-part Know Your Land series, Dr David Wingate explores our native forest in celebration of the United Nations International Year of the ForestsAs this year has been declared the International Year of Forests by the United Nations it is appropriate to review the history of our forest heritage in Bermuda and to ask whether there is more we could do to protect and enhance what little is left of it. But first a word about the value of forests generally.Firstly, forests are the second most important reservoir of carbon sequestration after wetlands (such as marshes). As such their conservation and restoration is going to be vital in the battle against global warming which has been largely caused by increases of carbon dioxide released by the burning of fossil fuels (such as gasoline and diesel) and forest clearance.Secondly, forests are great stabilizers of climate, dampening extremes of temperature and helping to store water and to slow runoff and erosion.Thirdly, the three dimensional and complex structure of forests makes them the greatest reservoirs of our planetary biodiversity which includes many economic resources such as timber, especially in the tropical rainforests.Fourthly, and this aspect is especially relevant in Bermuda, woodlands provide windbreaks against storms and against salt spray on coasts and help to screen developments, improve aesthetics and provide cool shade for recreation.As we have known since first discovery, Bermuda's benign subtropical climate and abundant rainfall created an environment in which forests were the dominant vegetation type covering the whole Island, but the dominant components of that forest were drastically modified and degraded by man's impact over the centuries following human colonization.Initially that forest was dominated by Bermuda cedar and Bermuda palmetto and southern hackberry in about equal abundance with a small diversity of other woody shrubs and trees, notably Bermuda olivewood, yellow wood, Forestiera, white stopper, buttonwood and wax myrtle forming dense thickets on hilltops, coastal slopes and peat-filled wetlands respectively. Mangrove forests likewise dominated salt lagoons and sheltered bays.With extensive clearing for agriculture, much of the original forest diversity was lost as some species were less efficient at self seeding, especially in the presence of introduced rats which ate their seed, but this was compensated for by many new plant introductions, some of which became invasive, and by a greater predominance of the cedar. The cedar, in particular, thrived in the presence of man, because it is a pioneer forest tree, its seeds dispersed by birds.It re-colonized cleared areas more quickly than any other species. This process was aided by man too, because of the immense timber value of the cedar tree which provided all of our timber needs for housing, furniture and cooking fuel and even sustained a thriving ship building economy for two centuries.Unfortunately, the accidental introduction of an accumulating number of pest insects eventually put pay to the dominance of the native forest and to the cedar's dominance in particular.In one catastrophic decade (1946 1956) following the building of the airport which accelerated invasive pest introductions to Bermuda, more than 95 percent of that, by then, monoculture cedar forest succumbed to a scale insect epidemic.To be continued in September's Green Pages.For more information on the International Year of Forests,visit: http://www.un.org/en/events/iyof2011/