Panama's tropical environment supports an abundance of plants. Forests dominate, interrupted in places by grasslands, scrub, and crops. Although nearly 40 percent of Panama is still wooded, deforestation is a continuing threat to the rain-drenched woodlands. Tree cover has been reduced by more than 50 percent since the 1940s. Subsistence farming, widely practiced from the northeastern jungles to the southwestern grasslands, consists largely of corn, bean, and tuber plots. Mangrove swamps occur along parts of both coasts, with banana plantations occupying deltas near Costa Rica. In many places, a multi-canopied rain forest abuts the swamp on one side of the country and extends to the lower reaches of slopes in the other.