Rainforests: Biodiversity and Threats
Rainforests are some of the most interesting landscapes on the planet. They’re our oldest living ecosystems, with some having survived in their present form for over 70 million years. Interestingly, while they only take up 6% of Earth’s landmass, rainforests are home to half of the world’s flora and fauna species.
“A rainforest is simply an area of tall, mostly evergreen trees and a high amount of rainfall.”
These collections of ecosystems have even more interesting qualities. Rainforests help both humanity and the environment; through climate regulation, providing resources, and more.
However, these invaluable but fragile areas are under attack. These special forests are being degraded and deforested at rapid rates, due to industrial and agricultural development. In this article, let’s dive into the ecology behind rainforests, their fascinating biodiversity, and some ways we can monitor their threats.
There are two types of rainforests: temperate and tropical.
Temperate Rainforests are located in mid-latitudes and tend to have much milder temperatures than tropical ones. They’re mostly found in coastal/mountainous areas, and they’re not very biologically diverse. However, they’re extremely biologically productive due to less decomposition than tropical rainforests.
Biological productivity is defined as “the amount and rate of production which occurs in a given ecosystem over a given time period”. Basically, the dry matter or energy produced in rainforest areas.
In temperate rainforests, plants grow for long periods of time (ex. coastal redwoods in California), and they’re home to large mammals, small birds, insects, and reptiles.
Tropical rainforests are, in my opinion, a bit more interesting and will be the focus of this guide. They’re the most biologically diverse terrestrial ecosystems in the world, with the largest tropical rainforest being the Amazon. Their biomes are very unique and are composed of four main characteristics.
- very high annual rainfall: high humidity, consistent rain, varying wet and dry seasons
- high average temperatures: due to closeness to the equator, typical daytime temperature of 84°F, strong solar energy from direct sunlight
- nutrient-poor soil: nutrients aren’t stored for long, plants absorb nutrients decomposed organic matter quickly
- high levels of biodiversity: lots of species of organisms with different ecological roles, different rainforests have unique biodiversity
Let’s go deeper into these high levels of biodiversity!
Tropical rainforests are hugely biodiverse, which is crucial for the survival of their rainforests and our planet.
In case you’re unsure, biodiversity is the number and types of species within an ecological community. For example, the Amazon rainforest has 40,000 plant species, 1,300 bird species, 3,000 fish species, 427 mammal species, and 2,500,000 insect species. Several factors play into why rainforests have such high biodiversity, like high climates, massive sizes, and the canopy structures of trees.
An ecological role is the service/function that an organism provides to an ecosystem — for example, a bee’s ecological role is a pollinator! Ecological roles are almost like the value propositions of organisms; how they contribute to their ecosystem.
Combining these two ideas shows why organisms are so valuable for keeping tropical rainforests alive and prosperous. Their massive biodiversity, composed of tons of different species, each with different ecological roles, are all vital for rainforests. Interestingly enough, they’re also beneficial for the entire planet; environment and inhabitants.
The plants in tropical rainforests are important for global climate and medicine.
Tropical rainforests regulate weather through absorption and creation of rainfall, alongside their exchange of atmospheric gases. Rainforests also affect the reflectivity of Earth’s surface; which then influences global weather. If rainforests are destroyed, weather patterns could become more unstable and extreme.
“Albedo” is the measure of light and heat reflected back into space from the earth’s surface. Lighter colored materials, like snow, have a higher reflectivity than the dark colors of a rainforest’s agriculture. Instead of reflecting light and heat, agroforestry in tropical rainforests absorbs more heat than soil. This heat carries moisture from forest trees into the atmosphere, where condensation produces rain. The evaporated moisture forms clouds, which reflect sunlight into space → keeping Earth cooler.
Therefore, tropical rainforests cool local climates and help generate rainfall. Less rainforests means less heat absorption, meaning less rainfall generation and cooling.
Furthermore, the flora from tropical rainforests, like the Amazon, have important medicinal benefits. According to the Rainforest Alliance, compounds in rainforest plants are already used to treat malaria, heart disease, bronchitis, hypertension, rheumatism, diabetes, muscle tension, arthritis, glaucoma, dysentery, and tuberculosis, among other health problems. 70% of all plants with anticancer properties only exist in the Amazon.
Here are some examples:
- Wasai → the root of the Wasai tree is great for kidney health
- Lapacho → used to treat cancer, alleviates pain from chemotherapy, can fight infections
- Canellila → treats ovarian cysts, believed to increase likelihood of conception
- There could be more but we haven’t explored enough!
Fungi species help regulate plant populations and could be the future of tackling garbage.
Fungi play key roles in tropical rainforest environments as mutualists, saprotrophs, and pathogens.
- Mutualists → two or more species benefit from interaction
- Saprotrophs → organisms that feed on decaying organic matter, decomposers
- Pathogens → a microorganism that can cause disease (which is important here!)
Their interactions with trees can influence carbon and nutrient cycling, as well as the maintenance of biodiversity. Mycorrhizal fungi can improve plant nutrient uptake and accessing organically-bound nutrients.
Fungi can also break down organic material and make them available for plant growth. We see the high biodiversity of these organisms in tropical rainforests due to the huge range of forest micro-habitats, alongside favorable climate (hot, humid) conditions.
A specific, crucial ecological role that fungi provide is behaving as “biodiversity police” — controlling population sizes of biodiversity. This prevents species from dominating and unbalancing the rainforest. Because of this, microscopic fungi and microbe species are equally as important to the survival of rainforests as flora and fauna.
To do this, fungi spread quickly between closely packed plants of the same species, preventing them from becoming a dominant species and allowing more species to flourish. These small fungi between plants control population sizes for plants across the entire rainforest.
These fungi are microbes that live on plant microbiomes, forming symbiotic relationships and maintaining population size when needed. The huge amount of vegetation species richness comes of these contributions from fungi.
Rainforest fungi are also important for the planet — a rare species of mushroom found in the Amazon, called “Pestalotiopsis microspora”, survives on eating plastic. They can convert polyurethane, a common plastic compound, into organic matter. Imagine the potential for waste reduction through leveraging this cool ability!
There are more microorganisms, but we don’t know too much about them yet.
In tropical rainforests, microbial processes occur at a tremendous scale. There’s a huge amount of decomposers on the forest floor, including bacteria, fungi, termites, who break down the nutrients in organic matter. This process is aided by the Mycorrhizae fungi, which works in mutualism with plants. they attach to plant roots and help uptake roots more efficiently. They’re mutualists because both organisms benefit: plants provide fungi with sugars and starch in return for ‘their service’. Mycorrhizae may also help plants resist disease and drought!
Unfortunately, we don’t know too much about the microorganisms in rainforests and their specific ecological roles, due to a lack of exploration. Here are some key types scientists have discovered so far:
- acidophilic bacteria
- actinomycetes
- mycorrhizae
- fungi
- protists
Mammals are also very useful for plant prosperity.
You’re probably used to bees, hummingbirds, and maybe even bats as pollinators — animals important for plant reproduction. However, in tropical rainforests, several other unique mammals are also responsible for this process. Plants attract them through a concoction of specially designed traits, like alluring scents, flashy colors, and nutritious pollen. Seed dispersion is another ecological function some rainforest mammals provide. Lemurs pollinate palm trees in Madagascar, and Borneo’s fig trees have their seeds dispersed by orangutans.
The different species in the rainforest are critical for habitat survival and planetary health, due to the ecological services they provide.
Unfortunately, tropical rainforests are under attack.
Damming, invasive species and logging are two huge threats to tropical rainforests, specifically the Amazon. Let’s dive into these issues from an Amazonian perspective, and potential means for solutions through monitoring biodiversity!
Monitoring Biodiversity
Biodiversity is measured as an attribute of two components: richness and evenness. Richness refers to the number of species within the rainforest and their population sizes, whereas evenness means the proportions of species present in an ecosystem. The more proportionally equal species are (similar population sizes), the greater the evenness.
Biodiversity is measured and monitored because high diversity is seen as synonymous with a healthy ecosystem. Generally, biodiverse communities are thought to be more stable, productive, and resistant to invasion. However, there are a couple of downsides.
There are specific benefits to ecological communities directly from high plant biodiversity: forage for insect and vertebrate species, environmental stability, potentially useful genetic material, and reducing likelihoods of ecosystem invasion.
Spatial Biodiversity Metrics:
- alpha diversity → richness and evenness of individuals within a unit/area
- beta diversity → biodiversity differences when comparing habitats
- gamma diversity → diversity of habitats within a unit/area
We know that tropical rainforests are highly biodiverse (beyond precise counting), so measuring all populations rigorously doesn’t make sense. Instead, I think it makes more sense to monitor and measure specific species within Amazonian rainforest habitats.
Damming
Large, well-backed hydroelectric projects in the Amazon rainforest have led to massive environmental losses. Unfortunately, these dams are often inefficient because of their basin design — meaning that these huge areas of rainforest are taken over by a system ineffective at electricity generation. Also, there are very high carbon emissions from these renewable dams, so the benefit over fossil fuels isn’t prominent.
Not only do these dams kill off local wildlife, but they can also destroy aquatic habitats and fish populations, displace indigenous people, and emit carbon dioxide. Dams alter water chemistry (nutrients are lost) and affect fish passage → an unfriendly combination for inhabiting organisms.
Tons of damming is happening in Brazil, driven by national agricultural and industrial interests. Fueled by renewable energy potential, effects on the rainforest environment and indigenous peoples are being disregarded. This is because the country’s civilians rely on these dams; with 75–80% of their electricity coming from hydropower.
A major example of a dam in the Amazon rainforest inside Brazil is the Belo Monte dam, the world’s fourth-largest hydroelectric project. This dam blocked the Xingu River, a major Amazon tributary. In 2015, the reservoir flooded 260 sq mi of lowlands and forest, displaced 20,000+ people, extensive damage to river ecosystem (500+ fish species, many unique). Unfortunately, Brazil is in the process of building even more of these damaging dams.
There’s an abundance of species threatened by damming in the Amazon. Aquatic and terrestrial species that rely on fast-flowing river segments are greatly at risk because these are often the areas targeted for hydropower projects. These species will all have altered habitats due to dams, and are some are likely to be wiped out.
- affected aquatic species: turtles, dolphins (river dolphins), otters (giant river otter)
- affected terrestrial species: monkeys
Many dams are also planned in neighboring Amazonian countries, like Peru and Bolivia, also with major environmental impacts.
Deforestation
Since 1970, over 600,000 square kilometers of the Amazon rainforest have been destroyed. Today, 40 football fields worth of the forest are cleared each minute.
Loggers often use false permits, ignore restrictions, cut protected species and steal from protected/indigenous areas → these operations are hard to monitor and detect because they’re small-middle scale without much supervision, alongside a complex chain of custody in the supply chain. Legal restrictions of logging operations are difficult to make effective because of the quantity and remoteness of them.
For example, in Colombia, illegal practices have been reduced, but 80–90% of all logging activities done are still illegal — with timber being smuggled to other countries.
Forest trees are super important for habitat survival and climate regulation, so logging is detrimental to these two things. Due to deforestation, tropical rainforests have become net carbon emitters → releasing more CO2 than what’s absorbed. Unfortunately, deforestation is directly dangerous for fish species → without trees holding soil in place, it washes into rivers and smothers fish (erosion).
Other species are also harmed by deforestation:
- iquitos gnatcatcher → only 75–374 individuals left in the wild
- giant brazilian otter → estimated wild population of 1000–5000
- white bellied spider monkey → population has declined by at least 50% in the last five decades.
Invasive Species
One of the biggest causes of environmental disturbances, like the decline in pasture productivity and biodiversity losses, is the presence of herbaceous weeds → an invasive species. These dangerous plants are the main invasive species present in the Amazon region and are a major threat to its vegetative biodiversity. Some examples are Vismia Guianensis, Paspalum Virgatum, Mimosa Pudica, Senna Obtusifolia, and Cyperus Rotundus.
Monitoring Species
A potential way to address these issues is by measuring biodiversity.
Monitoring Animals Endangered by Deforestation:
The metrics would be the population size of species and population density. ‘Mark-and-recapture’ as well as ‘quadrats’ are potential ways to obtain these measurements
- mark-and-recapture: A portion of the population is captured, marked, and released. Later, another portion will be captured and the number of marked individuals within the sample is counted.
- quadrats: sampling population sizes in a small area of a habitat to estimate local distribution of that species
Monitoring Forestry in Remote Locations to Prevent Deforestation:
Monitoring forest cover and estimating density and local populations of forests, monitoring, and identifying missing tree regions.
Monitoring Herbaceous Weeds, the Invasive Species
Monitoring and mapping geological spread of these weeds to approximate damage, predict the further spread, and estimate population sizes could be an important way to supervise vegetative prosperity in the Amazon rainforest.
Rainforests are awesome, and they’re important for so many things humans rely on. However, deforestation, damming, and invasive species are massive threats to their survival. I think, through measuring biodiversity, we can begin taking a data-driven approach to solving these issues. Therefore, saving the rainforests.
Thanks for reading!
