Keeping our forests, peatlands, grasslands, parks, and other green areas intact is vital if we want future generations to have at least the same quality of life we have now. They capture carbon dioxide and toxic emissions, while providing food and habitats for animal species worldwide. For example, forests shelter 80% of known amphibian species, 75% of known bird species, and 68% of known mammal species [including many endemic species that don’t live outside of specific forests]. Additionally, 2.4 billion people rely on wood-based energy for cooking.
In 2019, forests covered around 37% of habitable land [with shrubs accounting for an additional 11%], but that’s dropping fast. From 1990-2020, the world lost a net 1.78 million km2 of forests, despite large forestation projects and natural forest expansion taking place. For reference, Mexico’s surface area is around 1.94 million km2.
While natural hazards like wildfires can certainly cause important forest degradation, they’re not responsible for a whole lot of deforestation [i.e. degradation implies forests can recover, whereas deforestation implies that land use conversion occurs]. Consequently, with most of actual deforestation being caused by humans, it’s pretty clear that reducing deforestation worldwide is up to us – not Mother Nature.
Of the 60,000+ known tree species, over 20,000 have been placed on the IUCN Red List of Threatened Species. Over 8,000 of these are classified as globally threatened – of which over 1,400 are listed as “critically endangered and in urgent need of conservation”.
Since we’ll always need wood for a variety of uses, we can’t just suggest banning all types of deforestation. However, to mitigate climate change and reduce biodiversity loss, the entire world [as opposed to just a couple continents now] will have to transition to sustainable deforestation. Meanwhile, it’ll be up to us to reduce our dependence on wooden products, since sustainable deforestation can’t supply enough wood for our current global demand.
Between mining, urban expansion, food production, severe wildfires, and now unsustainable logging, we’ve seen why deforestation occurs. As such, in this section we’ll concentrate on how it affects us instead.
Deforestation causes significant biodiversity loss for plant species and habitat loss for animal species – which inevitably induces even more biodiversity loss.
Intensive agriculture has reduced our food selection to only a few genomes per species [e.g. with monocultures], which has made entire food systems vulnerable to a few pests, weeds, or diseases. Hidden in forests are the other genes for these species, such as wild carrots, eggplants, peaches, and many more crops that local biodiversity depends on. By destroying forests worldwide [e.g. to expand agricultural land], we’re reducing gene diversity and thus weakening global food security.
Unfortunately, biodiversity loss due to deforestation also weakens ecosystems, which can have adverse effects on food security as well – since biodiverse ecosystems ensure greater climate-resistance for our food systems [e.g. tree roots reducing soil erosion, animal pollinators, mangrove-protected shorelines]. And that would be helpful moving forward as we look to mitigate climate change’s impacts.
However, it’s about more than just genomes and climate-resilience. Food from forests accounts for roughly 0.6% of global food consumption. That doesn’t sound like much, but then again there are close to 8 billion people on Earth. And since underdeveloped countries usually consume less food per capita and tend to rely on food from forests more than developed countries, the contribution of highly nutritious forest foods to global food security can’t be overstated.
At this stage, a common question is: if the ecosystem is all about the survival of the most adapted, can’t it just find a new balance? Well, there’s some good reasoning there, but statistics show that the environment isn’t nearing any kind of sustainable balance. On average, the population sizes of mammals, birds, fish, amphibians, and reptiles have dropped by 68% since 1970. Ecosystems aren’t adapting to lower populations – they’re just continuously losing biodiversity. So no, ecosystems aren’t reaching a balance, they’re in a full transition.
But a transition to what? Well, until we stop emitting GHGs into the atmosphere, encroaching on natural lands, and polluting ecosystems worldwide, the answer to that question will keep changing. The safest answer might simply be “a transition to new ecosystems” that have different characteristics and balances. That sounds pretty stable, but we can’t forget that humans are adapted to the current environment. The last thing we want is the natural world changing in ways that seriously damage our quality of life or viability as a species. And let’s not forget that we’re centuries away from ecosystems reaching any kind of balance if we keep emitting GHGs until 2050.
The ‘transition phase’ we’re in right now is not a pretty one. Our unsustainable ways are modifying the Earth’s living conditions so quickly that we’re making the planet unlivable for the vast majority of species. Instead of having centuries to adapt to minor changes through random natural selection, species now have decades to adapt to major changes. This is causing more than just biodiversity loss – it’s causing the Earth’s 6th mass extinction. Until we start understanding that we depend on the natural world much more than it depends on a single species like humans, this ‘Anthropocene’ extinction will show no signs of slowing down.
Protecting existing natural areas and restoring lost biodiversity are 2 important tasks we’ll have to get better at to avoid further damage to ecosystems. Counting the number of trees and ensuring that forestation rates equal deforestation rates isn’t good enough. Instead, protecting primary forests, reducing demand for wood, and only logging planted forests have to be priorities to minimize biodiversity loss caused by deforestation. The IPCC suggests conserving 30-50% of the Earth’s land, freshwater, and ocean areas. As of 2022, protected areas represent less than 15% of the land, 21% of the freshwater, and 8% of the ocean on Earth.
What we’ve seen so far is what we’ll call the direct effects of deforestation [e.g. biodiversity loss, food insecurity]. Unfortunately, there are countless other indirect effects. These aren’t as obvious as the ones we’ve stated above [although they can be just as impactful], but we need to understand these effects to grasp the importance of forests and vegetation at the local and global scales.
As we’ve seen a few times already, forests are incredible carbon sinks [even if other green ecosystems like peatlands are much better sinks]– meaning they can absorb high amounts of carbon from the atmosphere. When we release CO2 into the atmosphere, vegetation and the ocean typically sequestrate 25% each, leaving the remaining 50% in the atmosphere. Of the 25%, trees typically absorb the most compared to other vegetation types, since they can store lots of carbon in their wood [which is why burning wood isn’t great, emission-wise]. Both plants and trees can help sequestrate carbon in the soil as well, by pulling in the atmospheric carbon during photosynthesis [also counted in vegetation’s 25%].
However, while deforestation certainly doesn’t make forests better carbon sinks, it can have some good offsetting effects – from a pure GHG standpoint. For example, if wood is used instead of cement during construction, then that could lead to a decrease in GHG emissions, since cement production is extremely carbon-intensive.
Toxicity Filters in Urban Settings
Trees can improve air quality considerably in urban areas, which can have positive impacts on health and pollution control. Trees absorb gases or stick toxic compounds to their leaves, removing them from the atmosphere. Precipitation can then flush these pollutants off the leaves and into the soil or the wastewater stream, where they go through a water treatment process. The tree leaves can also end up buried come autumn, keeping the pollutants far away from the atmosphere.
In any case, it’s important to understand that different trees absorb different compounds in different proportions. We have a good idea of which trees absorb which pollutants the most – but we can’t just plant a single type of tree to absorb large quantities of a specific pollutant, for many reasons. The following arguments are adapted for forestation in urban settings, but many still apply for tree planting efforts in natural environments.
First, planting a single type of tree is referred to as a monoculture forest, which has disastrous consequences on ecosystems for numerous reasons that we’ve already discussed.
Next, a single type of tree can facilitate invasive species, since it might be a pest’s favorite food. Especially if it’s a foreign tree, since we don’t know how it will react in the new environment. Sticking to native trees is often a safe bet, although not a guaranteed best solution – as we’ll see in the next point.
Lastly, the tree might not take to the ecosystem, whether that’s caused by the urban soil characteristics [e.g. salty pavements in winter], temperature changes [e.g. native trees might not be adapted to their ecosystem anymore], or pests and diseases. In any case, there’s no point in planting a tree if it’ll die in a few years’ time. As such, it’s suggested that a single species never exceeds 10% of a city’s total tree population [although monodominant tree families are quite common in natural environments– but not a problem since those ecosystems have been naturally evolving toward monodominance].
Getting urban tree planting right is trickier than it looks and requires many local experts and tree types. And it’s more complicated than just picking the right tree. Urban trees need to be located in the right spots as well or they could end up having negative effects on air quality, by trapping harmful pollutants in certain zones. We also need to consider if any of the trees’ emissions [such as allergens] can lower air quality by reacting with the environment.
With that in mind, cities that actually have the resources to find experts on the matter should take advantage and plan for a greener future. Getting it done right can have great economic benefits as well, as they can help large cities save hundreds of millions of USD every year by absorbing pollutants and reducing precipitation runoff during storms [among other benefits].
Trees and Water
Trees and other types of vegetation do a terrific job of lowering precipitation runoff. In urban areas, they can be used to help out water management systems by increasing water infiltration and retention rates in urban soil. This process can filter pollution as well, since polluting runoff infiltrates layers of soil where different processes clean the water [e.g. physical, chemical, or microbial filtration].
Tree leaves can also help reduce soil erosion from rainfall. Soil erosion is a significant problem in urban areas, since soil is damaged/lost and water infiltration rates could then decrease. This could lead to increased runoff, potentially causing floods if the water management system doesn’t adapt for such changes. Soil erosion can also increase/decrease sedimentation in water streams, which can aggrade/degrade river channels, increasing flood likeliness [aggrade = elevate the river floor]. The sediment flow can also reduce the population sizes of marine biodiversity when altering the river’s characteristics.
To recap, deforestation can cause an ecosystem’s soil to dry up. It can also increase runoff, induce floods, and aggrade/degrade rivers depending on local sedimentation characteristics.
On top of this, trees are important players in the global water cycle. Forests are responsible for a significant share of water vapor released into the atmosphere, through evapotranspiration [combines plants’ transpiration with wet soils’ evaporation]. Near recently deforested areas, clouds aren’t forming where they used to, since the evapotranspiration rates have changed. That means precipitation doesn’t occur when/where it should, or only in different proportions.
Water is kind of essential for most ecosystems, so deforestation can really end up destroying multiple ecosystems at once [a change in precipitation cycles is what we’d call climate change – it doesn’t have to involve global warming]. Rivers also depend on steady rainfall patterns, so changing the quantity of water they receive doesn’t sound like a great idea. Especially when thousands of ecosystems and billions of people depend on rivers to survive.
Forests are much more important to numerous global balances than we give them credit for, but if we keep on logging away – we’ll realize very quickly how valuable they were.
Honorable Mention: Increasing Human-Wildlife Contact
Due to the significant biodiversity content of forests and the current rates of deforestation, human-wildlife contact has been on the rise as of late. In most cases, habitat loss has pushed wildlife deeper into the forest, where it either adapts to the new environment [potentially creating invasive species] or dies. However, wildlife doesn’t always migrate into another natural environment far away from humans – which can increase the likeliness of human-wildlife contact. This can create loads of problems, including the threat of animals passing along deadly viruses and diseases to humans. And as we all know too well, that can have pretty serious consequences at the global scale.
A COUPLE MISCONCEPTIONS
Trees don’t help reflect much radiation back toward the atmosphere [i.e. they have low albedo]. As such, some trees that don’t capture a great deal of CO2 over their lifetime can actually increase the carbon content of our atmosphere. This is another reason why we must be careful before jumping the gun on a poorly planned afforestation program [afforestation is just forestation on previously non-forested land].
Especially in northern climates. Even when the tree species have been carefully picked to integrate their environment well, massive afforestation projects in these areas risk covering highly reflective snow with a less reflective tree canopy [e.g. for evergreen trees].
Forests don’t really produce much oxygen, contrary to popular belief. For example, the Amazon rainforest isn’t responsible for 20% of oxygen production worldwide, in fact it barely provides any oxygen to the rest of the world. It’s responsible for 6-9% of global oxygen production – that’s true – but the Amazon and its microbes end up consuming nearly all of that on their own. Nonetheless, being self-sufficient is still pretty cool since it leaves more oxygen for the rest of us.
So the good news is that wildfires don’t really endanger our oxygen supply, they only release billions of tonnes of CO2 stored in biomass and soil into the atmosphere every year.
SPECIAL WATER FORESTS
Land only represents 29% of the Earth’s surface, yet holds countless ecosystems that are essential to the Earth’s balance. We’ve gotten pretty good at studying terrestrial environments – although there’s still much to be done there. Oceans, on the other hand, we know much less about. One thing we know for sure is that they too hold diverse ecosystems that play an extremely important role in keeping the Earth’s conditions stable.
There are some MVPs out there in the oceans [Most Valuable Players]. Certain aquatic ecosystems are essential to maintaining biodiversity and mitigating climate change, just like forests are. Unfortunately, most share another similarity with forests. They’re headed for extinction because of humans, threatening irreversible damage to natural environments around the globe.
The rest of this section will cover a few of these aquatic MVP ecosystems – including their strengths and threats.
Mangrove ecosystems are coastal, semi-aquatic, swamp-like areas that take advantage of the tide. At high tide, they look like regular trees that just grow in water instead of on land [usually in marine water, but freshwater can work too]. At low tides however, the beauty of the mangroves appears as the water tides away from the ground surface [although some mangrove roots are always submerged]. Above the wet ground, the strangely shaped mangrove roots stick out, creating countless small tipis of roots.
Mangroves support high biodiversity by providing all these advantages for an enormous range of species. They’re responsible for boosting the population sizes of all types of marine life considerably. Larger populations mean local communities and seafood corporations can return home with better fishing yields, increasing food security. Mangroves can even provide habitats for corals, since they can offer protection and colder waters. In fact, mangroves help out many other marine ecosystems, by being both a source and deposit for their nutrients/sediments.
Mangroves are also very important carbon sinks. On top of storing more carbon than almost any other ecosystem per given area, they store most of this carbon below ground in the roots or soil – which is great. Trees that mostly store above ground are weaker carbon sinks, because the CO2 stored in the wood or leaves can resuspend in the atmosphere during decomposition when the tree dies or leaves fall. Below ground storage allows for better sequestration as the CO2 is usually confined in the ground.
Mangroves’ deep roots are also great for stabilizing coastlines and reducing soil erosion with their intertwining root systems. Their high forest density and soil infiltration rates also help protect coastal communities from floods, waves, and even tsunamis.
Unfortunately, we’ve been putting mangrove ecosystems under lots of pressure. From 1990-2020, mangrove area decreased by 6.6% worldwide, although the rate of deforestation has improved in recent years. In the longer term, severe sea level rise due to global warming is a major threat for mangroves, as coastal areas will be the first ones hit.
Coral reefs are made up of plenty of tiny animals called polyps that eat microscopic prey. As polyps grow, ‘hard corals’ build hard shells around their jellyfish-like bodies to protect themselves from predators. Most corals are also symbiotic with algae, meaning algae is living and growing inside of the corals [like Venom from Spiderman]. During the day, algae supply polyps with energy from photosynthesis, allowing the corals to grow toward sunlit areas where algae will strive. At night, polyps supply themselves with energy by eating microscopic prey. Hard corals grow in a variety of strange shapes, leaving hard shells filled with colorful algae behind as they grow toward the surface.
When corals form systems over great distances, they become part of a coral reef. Coral reefs, like mangroves, are extremely important for the surrounding environment. They are one of the most biodiverse ecosystems in the world, providing a home to an estimated 25% of all marine species on less than 1% of the ocean floor.
Over thousands of kilometers, coral reefs shelter many species from predators during childhood. They also provide food for some of the smallest aquatic animals on Earth, which is incredibly important to maintain biodiversity. By feeding the lower animals of the food chain and ensuring most of them can spawn in peace, corals are indirectly feeding the bigger fish. And if we follow the food chain all the way up, that means us too. Just like mangroves, a safe and nutritious ecosystem leads to strong biodiversity and large populations of marine species. In turn, that leads to better seafood yields for locals and fishing companies alike – as long as we avoid overfishing and leave nursery areas alone.
Shallow water coral reefs are also essential wave barriers. They can reduce wave energy by up to 97%, reducing soil erosion in coastal areas and protecting shorelines from storm waves and currents. By reducing soil erosion, they can protect mangrove ecosystems as well.
Tourism, fisheries, and coastal communities benefit from all coral reefs have to offer. In fact, reefs have an estimated value of $375 billion USD worldwide, as over 500 million people depend on them for food, protection, income, or recreation. Unfortunately, many corals and their reefs are dying. In 2021, the NOAA’s endangered species list featured 5 coral species, while 23 other species were listed as threatened.
Corals are extremely sensitive and can die for numerous reasons. When they die, corals that are symbiotic with algae ‘bleach’. Coral bleaching is likely to occur when the surrounding environment changes – so climate change isn’t helping.
When the waters near reefs change temperature or salinity [to name a few parameters], corals instinctively stress out the colorful algae from their system. If the corals remain stressed for too long, they eventually starve to death without their symbiotic energy source – and their rocky white skeletons [for hard corals] end up covering the ocean floor for years. The problem with this type of bleaching is that it depends on the surrounding environment’s conditions. As such, huge sections of reefs can die at once, since they all experience the same changes.
From 1998-2017, the Great Barrier Reef in Australia [largest reef in the world] suffered 5 mass bleaching events due to abnormally warm ocean surface temperatures. During the same span, it also saw 2 freshwater bleaching events due to summer floodwater discharging nearshore. Between 2016 and 2017, 2/3 of the Great Barrier Reef was affected by temperature-driven bleaching events – and half of the entire reef bleached to death.
Global warming and climate change are increasing global ocean temperatures and the likeliness of extreme weather events. If we fail to keep global temperatures below the +1.5°C goal, we risk destroying these ecosystems beyond repair, and all their benefits will be lost. That includes the benefits that would be real useful to mitigate climate change, like reducing wave intensity to protect coastlines from soil erosion and flooding.
Due to climate change, reefs haven’t had a chance to recover between mass bleaching events. Severe regional bleaching used to occur every 27 years before the 1980s, but that figure has since dropped to every 6. A significant problem when you consider that harshly damaged reefs take a minimum of 10 years to recover – if no other bleaching events take place during that time span.
Algae [Not Really Headed for Extinction]
Algae are much more than just symbiotes for corals. With so many different types and sizes, these living things [can be plant or animal] were some of the earliest organisms on Earth. The plant types of algae are photosynthetic. When the Earth’s atmosphere was dominated by CO2 in its early days [likely due to high volcanic activity], algae went on an absolute tear and converted much of that CO2 into O2 – into the familiar 21% we know today.
Nowadays, algae are responsible for 50-80% of annual oxygen production worldwide. Unfortunately, marine life consumes around the same amount of oxygen every year, so the algae doesn’t really help us out for O2 production.
Algal blooms [large fields of algae] can grow when algae have access to too many nutrients. In some cases, algal blooms can even start producing toxic compounds and form harmful algal blooms [HAB] that harm marine life and terrestrial species that depend on the water source [e.g. birds, mammals, humans]. In early 2020 for example, over 300 wild elephants died from cyanobacteria toxins in their drinking water – after harmful blooms of green-blue algae grew out of proportion. These types of events will occur more frequently as global temperatures continue to rise, since blue-green algae thrive in warm environments.
Humans are responsible for significant nutrient pollution in water bodies around the world, and that can cause algal blooms to form [this process is called eutrophication]. Harmful or not, blooms can end up killing everything in their surroundings. When blooms die [e.g. because eutrophying nutrients are completely used up], their decomposition process consumes so much oxygen that the blooms create ‘dead zones’.
Without sufficient O2 available [i.e. hypoxia], marine life is forced to evacuate the area, or if it can’t – die [leading to even more hypoxia]. Decomposing algal blooms also release loads carbon dioxide at once, which causes severe acidification surrounding the bloom [although it doesn’t really ‘add’ CO2 to the carbon balance since the algae is just re-emitting what it absorbed during growth].