Surtsey will survive are based on the rate of erosion seen up to the present day. Assuming that the current rate does not change, the island will be mostly at or below sea level by 2100. However, the rate of erosion is likely to slow as the tougher core of the island is exposed: an assessment assuming that the rate of erosion will slow exponentially suggests that the island will survive for many centuries. An idea of what it will look like in the future is given by the other small islands in the Vestmannaeyjar archipelago, which formed in the same way as Surtsey several thousand years ago, and have eroded away substantially since they were formed. Biology Settlement of life A classic site for the study of biocolonisation from founder populations, Surtsey was declared a nature reserve in 1965, while the eruption was still in progress. Today only a few scientists are permitted to land on Surtsey; the only way anyone else can see it closely is from a small plane. This allows the natural ecological succession for the island to proceed without outside interference. In 2008, UNESCO declared the island a World Heritage Site, in recognition of its great scientific value. Plant life In the spring of 1965, the first vascular plant was found growing on the northern shore of Surtsey, mosses became visible in 1967, and lichens were first found on the Surtsey lava in 1970. Plant colonisation on Surtsey has been closely studied, the vascular plants in particular as they have been of far greater significance than mosses, lichens and fungi in the development of vegetation. Mosses and lichens now cover much of the island. During the island's first 20 years, 20 species of plants were observed at one time or another, but only 10 became established in the nutrient-poor sandy soil. As birds began nesting on the island, soil conditions improved, and more vascular plant species were able to survive. In 1998, the first bush was found on the island—a tea-leaved willow (Salix phylicifolia), which can grow to heights of up to . By 2008, 69 species of plant had been found on Surtsey, of which about 30 had become established. This compares to the approximately 490 species found on mainland Iceland. More species continue to arrive, at a typical rate of roughly 2–5 new species per year. Bird life The expansion of bird life