Forests on the coastline are composed mostly of salt-tolerant mangrove trees, while the more sparsely populated inland has forests opening onto a plateau of drier grasslands. The climate is equatorial, with significant rainfall during the May–October rainy season and harsh harmattan winds the remainder of the year. Liberia possesses about forty percent of the remaining Upper Guinean rainforest. It was an important producer of rubber in the early 20th century. Four terrestrial ecoregions lie within Liberia's borders: Guinean montane forests, Western Guinean lowland forests, Guinean forest-savanna mosaic, and Guinean mangroves. It had a 2019 Forest Landscape Integrity Index mean score of 4.79/10, ranking it 116th globally out of 172 countries.