The existence of “jungles” in America depends on the definition used and the specific region discussed. The popular image of a jungle corresponds to a dense, tropical environment widespread across the Western Hemisphere. Scientists generally refer to these ecosystems as “rainforests,” which are classified based on climate and location. Understanding this terminology helps map where these biodiverse forests are found, from the tropical expanses of South America to unique systems within the United States.
Defining the Terms: Jungle vs. Rainforest
The words “jungle” and “rainforest” are often used interchangeably, but they describe two distinct ecological structures. A rainforest is a scientific term for a forest that receives high annual rainfall, typically over 1,750 millimeters, and features a multi-layered canopy structure. Tropical rainforests are found near the equator with consistently warm temperatures, while temperate rainforests occur in cooler, coastal regions.
The key feature of a mature rainforest is its dense, continuous canopy, formed by the crowns of tall trees. This canopy blocks up to 95% of sunlight from reaching the forest floor, resulting in a relatively sparse understory of vegetation. Walking through the understory of an old-growth rainforest is surprisingly easy because the lack of light inhibits thick growth.
In contrast, “jungle” is a less precise, cultural word for a dense, tangled area of vegetation. Ecologically, a “jungle” develops when a break in the canopy occurs, allowing sunlight to hit the forest floor. This influx of light fuels rapid, impenetrable growth of vines, shrubs, and small trees, creating thick undergrowth that is difficult to traverse. A true jungle environment is typically found at the edges of a rainforest, along riverbanks, or in disturbed areas.
Tropical Rainforests Across the Americas
The most extensive tropical rainforests are located across the Americas, primarily in South and Central American landmasses. The largest example is the Amazon rainforest, a biome spanning approximately 6 million square kilometers. This immense ecosystem covers territory within nine nations and holds a staggering amount of the planet’s biodiversity.
The Amazon is home to at least 10% of the world’s known species, including about 16,000 tree species. The forest releases billions of tons of water daily, influencing rainfall cycles across the South American continent. Localized areas of dense undergrowth are common within this region, particularly along river systems or in disturbed areas, creating extensive jungle-like environments.
Moving north, the Mesoamerican Biological Corridor (MBC) links habitats from southern Mexico through Central America to Panama. This corridor hosts an estimated 7% to 10% of the world’s terrestrial species. The MBC incorporates diverse ecosystems, ranging from lowland tropical forests to high-altitude cloud forests.
The region’s geography, situated between the Pacific Ocean and the Caribbean Sea, creates a mosaic of forest types. Sections like the Maya Forest (Mexico, Belize, and Guatemala) or the Darién Gap (Panama and Colombia) represent intact tropical forest segments. The presence of these extensive tropical biomes, many containing dense, secondary growth, confirms that the classic “jungle” environment is an extensive feature of the Americas.
The Unique Case of the United States
The contiguous United States does not contain a vast tropical rainforest like the Amazon, but it does contain several ecosystems that meet the scientific criteria for rainforests. The only tropical rainforest managed by the U.S. Forest Service is the El Yunque National Forest in Puerto Rico. This forest, covering nearly 29,000 acres, receives over 5,000 millimeters of annual rainfall in some areas and maintains a consistently warm climate.
El Yunque is a biodiverse ecosystem, home to multiple forest zones and endemic species like the Puerto Rican parrot. The state of Hawaii also contains significant areas of true tropical rainforest, particularly on the windward slopes of its main islands. Hawaiian rainforests are characterized by high endemicity, with over 90% of their native species found nowhere else.
The continental United States primarily contains temperate rainforests, defined by heavy rainfall but cooler, seasonal temperatures. The Pacific Northwest is home to the world’s largest area of coastal temperate rainforest, stretching from northern California through Washington state and into Alaska. This includes the Hoh Rain Forest in Olympic National Park and the Tongass National Forest in Alaska, dominated by Sitka spruce and western hemlock.
These temperate forests receive between 1,500 and 5,000 millimeters of precipitation annually. They are characterized by a massive biomass and a thick understory of mosses and ferns. Though distinct from tropical systems, these temperate forests are dense and often create challenging, jungle-like conditions on the ground. The United States and its territories possess both tropical and temperate rainforests.