Forests, the sloths’ home
Forests are areas of land covered with trees. “Forest” is a very broad term that encompasses many different types of ecosystems, varying degrees of tree density, tree type, and land management. The first fern-like trees appeared on Earth about 380 million years ago, and today forests are the dominant land-based ecosystem on the planet, with 45% of all forests on Earth being found in the tropics.
Forests come in three distinct categories
Temperate forests occur in temperate climes; areas with distinct spring, summer, autumn, and winter seasons, and low humidity levels. Most of these forests are found in North America and Europe.
Boreal forests, also called evergreen forests, are largely made of coniferous evergreen trees. They are characterized by extremely cold temperatures, and most such forests are found in North and East Europe, and Northern North America.
Tropical forests grow in tropical climates; they are widespread throughout places such as Southeast Asia, Western and Central Africa, Central and South America, the Island of New Guinea, and Australia. Tropical forests cover approximately 12% of the Earth’s surface.
Tropical forests, where sloths live
Tropical forests, often called jungles, are biodiversity hot spots. They produce almost 22 gigatons of biomass per year—talk about the opposite of a carbon footprint!
Tropical forest temperatures usually range between 21°C (70°F) and 30°C (86°F), with humidity ranges between 77% and 88%. Unsurprisingly, rain is frequent in tropical forests, reaching up to 1000cm (almost 33 feet) per year–however, due to the humidity and temperature, tropical forests produce their own rain, and up to 75% of water cycles within the forest, evaporating from and raining back down on the same ecosystem.
In spite of the comparatively small area they occupy, tropical forests hold 50% of the world’s biodiversity–and no one yet knows exactly how many species live there.
In addition to rainforests, tropical forests also include high elevation cloud forests, so called because of the near-constant presence of fog and mist.
This is due to lower temperatures that cause water to evaporate slower. As a result, cloud forests are very humid. Cloud forests exhibit much greater differences in elevation and topography than rainforests. The peaks and valleys contribute to the formation of “clouds”. Rainforests are warmer and found at lower elevations.
Rainforest Structure
Rainforests are split into four vertical layers, each possesses different features depending on the level of rain, light, and air circulation. The layers are mutually dependent on each other and work together to form a rainforest.
Emergent Layer
The emergent layer is the highest layer of the canopy, reaching up to 60m (200ft) tall, consisting mainly of thin branches and fewer epiphytes (plants that grow on other plants) than the lower layers. Sunlight in the emergent layer is consistent and abundant, however, the strong winds strip moisture from exposed leaves, so trees usually have a waxy top layer on these leaves to prevent wind chapping.
At this level, pollination occurs by the wind. The animals found at the emergent layer will be small and light, able to navigate spindly branches or flying creatures such as birds, including one of the main sloths’ predators, the Harpy Eagles.
Canopy Layer
Found beneath the emergent layer, the most densely populated section of the rainforest is the canopy layer–this is where most animals live, along with a large variety of epiphytes. The high density of leaves and branches in the 6m (20ft) thick canopy blocks a lot of the rain, wind, and sunlight from reaching the layers below.
As with the emergent layer, leaves in the canopy have developed a waxy surface to retain moisture, and have evolved a pointed shape that prevents water from collecting on them.
Most fruit in the rainforest is found in the canopy layer. Many plants use this method for seed dispersal, as the fruit attracts a wide variety of different species of birds, mammals, reptiles, and invertebrates.
Understory Layer
The understory lies beneath the canopy and above the forest floor. It is a dim area with little direct sunlight and very little wind. The understory is home to most of the flowers found in the rainforest. These flowers are big, brightly colored, and aromatic in order to stand out to pollinators in the low light of this layer.
Protected from the wind, the leaves found here are usually large, and it’s common to find many fenestrated (provided with openings or apertures) species, such as Monstera.
This layer is shielded from strong winds and the most intense rain by the canopy layer above, but still has adequate sunlight to make a perfect habitat for amphibians to maintain their moisture and thermo-regulation.
Forest Floor Layer
The darkest and lowest layer of the rainforest of the forest floor. Very little sunlight and less wind reach the forest floor, while rain trickles down after being filtered through the layers above. This makes it difficult for plants to grow there. Tree saplings struggle to grow tall enough to punch through the upper layers and into the sunlight.
The forest floor is where the building blocks of the rainforest originate. Leaves, branches, fruit, seeds, animal waste, and anything that starts out in the high layers of the rainforest eventually fall to the ground. Many small invertebrates assist in this decomposition and are preyed upon by larger animals and foragers. The forest floor is also home to tropical river ecosystems, which may be wide enough to allow sunlight to penetrate or may be narrow and shallow, and dark.
As debris falls from the trees and decomposes into the ground, nutrients vital for life are released into the soil, are taken up by the roots of trees, and eventually dispersed throughout the many layers of the rainforest.
Forests of Costa Rica
Costa Rica is mostly covered in tropical forests; it claims the title for largest biodiversity to landmass ratio, holding 6 – 10% of the world’s biodiversity, yet only 0.03% of the world’s landmass.
In 2020, it was reported that over 50% of Costa Rica was rainforest, but less than 25% of which was primary rainforest. 28% of Costa Rica is protected forest in the form of national parks.
Why forests are important to biodiversity, climate, and humans (and sloths)
More than three-quarters of Earth’s plant biomass is found in forests. This acts as an important regulator of climate, temperature and water cycle. Plants sequester carbon and produce breathable oxygen; a single full-grown tree produces an average of about 100 kilograms (220 lb) of oxygen per year.
Forests are also critical regulators of the watershed, acting as both water purifiers and flood control. They help stabilize soil, fix nitrogen, and prevent erosion.
Forests and humans
Humans have a long and sometimes complex relationship to forests. On one hand, they are necessary to the healthy functioning of Earth’s biosphere and provide many important resources, such as timber, fuelwood, and medicinal plants; on the other hand, the space taken by forests is often desired to feed urban sprawl and agriculture.
Many traditional societies rely on forests to provide all essential resources and their ways of life are severely threatened by increasing deforestation.
Additionally, forests are home to approximately 80% of Earth’s terrestrial animals. Rainforests in particular host almost half of all living animal species, two-thirds of all flowering plants, and more than one-quarter of all-natural medicines (discovered to date). They are also the only place in the world where sloths live in the wild.
Sloths and forests
Sloths are arboreal neotropical animals, meaning that they live in the trees of Central and South America. These trees must be rainforest trees that receive over 250cm (100in) of rainfall per year, provide a wide variety of tree types and leaves and have good canopy connectivity for sloths to move among.
Some sloths, such as the endangered pygmy sloth (Bradypus pygmaeus) only live in the mangrove forests of the Panamanian island Escudo de Veragua, while Hoffman’s two-fingered sloth (Choloepus hoffmanni) are more tolerant of a wide variety of forest habitats.
Ironically, the healthier a forest is, the harder it is to see the sloths! This is because an ideal rainforest habitat has tall, dense trees with a very connected canopy layer, which acts as perfect camouflage for our green, furry friends.
Deforestation threatens all of us: the planet, the people, and the sloths.
Illegal logging for hardwoods, slash and burn agriculture, and clearcutting for agricultural and urban sprawl are huge threats to tropical rainforests. Some estimates project that more than a quarter of all animal species could go extinct within the next 50 years if this level of deforestation is not halted.
There is good news though: if given half a chance, forests naturally renew themselves. Planted treelings send the message that open areas are not parking lots, canopy bridges give wildlife a safe way to continue being part of the ecosystem, and responsible ecotourism gives a financial incentive for struggling economies to invest in the future.
Sloths are an excellent umbrella species for rainforest ecosystems because when we save the sloths, we save the trees, and when we save the trees, we save the world, and when we save the world, we ultimately save ourselves.