Tree surrounded by greenery

Feeling green: What plants do for us

From helping keep cities cool to improving air quality, or keeping the world’s water cycle in check, we simply can’t live without plants.

The first plants as we might recognise them emerged hundreds of millions of years ago, before the dinosaurs and our first mammalian ancestors existed. After millions of years of single and then multi-cellular organisms evolving out of primordial soup, plants emerged as life forms capable of using sunlight as food.

Plants provide the core basis for life on Earth and they are the single most important pillar of human nutrition

Qu Dongyu, Director-General, FAO speaking to UN News

Plants are almost like the other side of the same coin that we find ourselves on: plants breathe in the CO2 we exhale, and without their contribution in a number of ways, life on Earth would be virtually impossible to sustain. Here are some of the ways we just can’t do without them in our world today.

The air we breathe

For most of Earth’s history, changes to our planet’s atmosphere were largely driven by long-running structural phenomena like volcanic activity or other such phenomena. The advancement of technology in the human era, including the burning of fossil fuels, has done much to release large amounts of carbon and particulate matter (PM) into the air. It’s posed a serious problem for human health, as such pollutants are toxic and can trigger a number of health conditions if inhaled or ingested in large amounts over time.

However, we’re now finding that trees are especially good at filtering out PM through their leaves. Larger-leafed trees are some of the best candidates for planting in urban areas if you want to minimise the risk of inhaling such pollutants – that’s because there’s a chance the trees will have either caught them on the hairs of their waxy leaves, or directly absorbed them. Elder, silver birch and yew trees are deemed most efficient at capturing PM, reducing PM levels by as much as between 70-79 per cent in wind-tunnel experiments.

Trees keep cities cool

If you live in a city, there’s a chance you might have heard of or at the very least experienced something called the urban heat island phenomenon. Directly caused by human activity, including energy consumption and use of cars, the centre of cities is very often much warmer than its surroundings. This is all compounded by the fact that hard, artificial surfaces are less capable of reflecting heat from the Sun, making city centres even warmer. However, there’s a role for plants to play in this urban jungle we find ourselves in.

Plants such as trees produce a large amount of natural shade, helping keep urban surfaces cooler for longer by protecting them from direct sunlight. The US Environmental Protection Agency (EPA) reported that trees help reduce temperatures on surfaces by 11-25 degrees Celsius if they are shaded by trees, as compared to peak temperatures seen on unshaded surfaces. As urban populations continue to grow, more of us would appreciate cooler surroundings, all made possible by our tall green friends. Benefits of cooler urban areas due to trees could mean less energy consumed by air conditioning, for example.

The cycle of water

The hydrological cycle is the relationship between ocean and land, and how water moves between the two in a constant pattern, from liquid to vapor and back again. Plants all play a role in helping regulate this cycle wherever they grow. We know that plant and tree canopies help capture moisture before it reaches the ground. Plant and tree roots are also very good at mopping up moisture from the soil and helping it sink deeper underground by storing it directly in their vast root systems. This helps prevent surface run-off, lessening the risk of flooding, when water persists above ground for longer.

In fact, trees are so useful, that the Woodland Trust estimates trees are 80 per cent more effective at preventing surface water run-off than the asphalt used to line roads. Allowing for more green spaces with plants and trees to grow allows for greater water infiltration as nature intended. The moisture captured in canopies helps allow more water to evaporate back into vapour, allowing more rain to fall, keeping the skies cooler and moister. More moisture in the skies helps prevent various places from becoming dry and lifeless over time.

Habitats for animals

Plants form the basis of survival for most life on Earth. Whether it’s smaller plants serving as a food source or larger ones such as trees serving as effective habitats and shelters, life on Earth simply could not survive without an abundance of flora. Plants don’t even need to be living to help animals survive; dead trees, known as snags, are often hollowed out remnants of old or dead trees, offering a place of protection for small animals and ideal breeding grounds for insects and smaller organisms. 

Animals such as beavers, for example, rely on dead wood and branches to form the basis of dams where they can protect themselves, hiding away from predators which stalk them in their environment. Plants are some of the most giving organisms on the planet, and from birth to death, they contribute to the good of the planet. In death, plants return to the soil from which they sprung, releasing natural fertilisers into it which nourish smaller organisms. Not only that, but this fertile soil allows even more plants to take their place, for other animals to eat or use to make into homes.

Holding back the desert

Admittedly, plants can’t exist in every environment. The scorching sands of the Sahara and the frosty tundra of the Arctic are barren in many places due to the temperature extremes among other things. Deserts are especially tricky places for plants to live, owing to a chronic lack of water and dry, dusty soil which lacks nutrients for them to use to grow. However, plants have a role to play in stopping the advance of such deserts. That’s because an abundance of plants, as mentioned already, keeps environments rich in water.

Plants also ensure an abundance in biomass, allowing the existence maintenance of fertile soil, much of it formed from decomposed plant matter. There is great value in preserving green spaces from desertification, but the Great Green Wall goes one step further. Established in 2007, this initiative is already in the process of ensuring the growth of flora across a stretch of land 8,000km wide, across the width of Africa itself, focused in the Sahel region. It aims to restore biodiversity to the region, improve access to clean water and generate jobs and growth for local inhabitants, giving Africa a prosperous, lush, green belt.

A blank canvas

One of the obvious uses for plants in the modern age is for the industrial scale of use as paper all over the world. Plants such as reeds formed the basis of papyrus, which the Ancient Egyptians used to write for centuries. Although not classed as a form of paper, papyrus established how plants could be stripped down into durable materials ideal for use in writing. Paper itself was likely invented in China during the Eastern Han era, with plant fibres and other materials were mashed together. Before the advent of paper, many had resorted to etchings or simple rags to convey the written word in an easily-produced medium.

The production of paper comes at an obvious cost to the environment: countless numbers of trees have been pulped all to produce mountains of paper over the centuries. Fortunately, any kinds of paper which aren’t glossy or laminated are considered biodegradable if they escape into the natural environment. Not only this, but paper can often be recycled so long as it is kept clean and not contaminated by other substances like glues or plastics. Provided we can transition away from needing trees to be pulped and recycle our paper more carefully, we can continue to make use of paper to capture our words, or perhaps simply switch to even greener options like going digital or paperless entirely.

A healing concoction

For millennia, generations of people have passed down the knowledge of how plants can be beneficial to human health. We know which plants are toxic and which ones could save our lives; nature has the power to harm or help us in equal measure. For example, willow bark was often turned into a fine powder by ancient people to administer as what we’d call a modern pain-killer. That’s because this bark contains a substance called salicin which reacts with our bodies much like aspirin, reducing inflammation and pain once absorbed into the bloodstream.

Plants are vital sources of nutrition to all animals, with many producing fruits rich in sugars, vitamins and minerals needed to maintain healthy bodies. Some plants have profound medicinal uses beyond anything our ancestors could have dreamt of. Many medicinal substances are found in the roots of plants, including ginger, ginseng, garlic and echinacea, while flowers such as chamomile and the leaves of plants such as ginkgo trees are all incorporated into modern medications available over the counter. While the jury is still out on whether there is conclusive evidence the likes of echinacea consumption can shorten the length of colds, plants are known great sources of antioxidants and anti-inflammatory substances.

The mouths they feed

Plants have always been and remain a core component which is necessary to sustain much life on Earth. The UN estimates that 80 per cent of the food we eat is plant matter, and calls plants the ‘core basis for life on Earth’. The most common plants we consume include crops such as wheat, maize and rice. It is believed that 50,000 plants in the world are edible in some way, and crops such as rice are the source of 90 per cent of the calories for people living in many low-income countries.

In the absence of animals reared for their meat, plants are a staple part of the human diet. Without them, we would starve and the animals we rely on for many things in life would also lack a source of food of their own. The ability to grow crops in an orderly way is one of the key moments in human civilisation, and we started growing plants like this at least 10,000 years ago, at the start of what many term the dawn of the Holocene era.

For most of the Earth’s history, plants grew whichever way they saw fit, influenced in part by the way animals moved around, but more or less without any sense of planning. The advent of farming created the concept of yields – how much food any given crop could be expected to produce in a given year. Early humans studied the seasons and saw how plants responded, and gradually began refashioning plants to produce higher yields. This, in effect, was a form of artificial selection, not yet genetic modification, but an understanding that certain kinds of plants grown in certain ways in prescribed places would feed more people for longer than others.

Fast-forward to today, and we have thrown off the shackles of having to live at a subsistence level. While our ancestors lived no more than 30 years on average in ancient times, and spent most of their lives struggling to feed themselves and their families, modern people enjoy a diet full of food sourced from plants with a significantly higher lifespan. Plant-based foods are highly nutritious and the global agricultural industry has grown to such a size that there are 570 million farms operating all over the world. According to Our World in Data, 72 per cent of farms are smaller than a hectare, and yet these patches of land provide a large amount of nutrition to the world.

Down to the root

Plants have never lived exclusively to serve the needs of humans or any other animal. They simply grow as they have evolved to do over millions of years, and some bear fruit to attract animals to help them procreate. Others germinate in more self-sufficient ways, and fossil records are rich in examples of beautiful and vibrant forms of flora, some of which have since gone extinct, but others which remain with us to this day. For example, did you know that Ginkgo trees are a good example of living fossils? These trees with their distinctive leaves have remained more or less unchanged over millions of years. In evolutionary terms, if it isn’t broke, it doesn’t need to be fixed.

Plants are something of a silent witness to the vast changes which have occurred on planet Earth, and have managed to persist despite the best efforts of asteroids, mass extinctions, ice ages and shifting landmasses. However, large-scale deforestation is a purely artificial phenomenon caused by human beings which plants simply cannot recover from, no matter how sturdy their roots may be. In addition, the growth in agriculture has had the unintended consequence of resulting in naturally-occurring plant life to be destroyed in order to feed a growing human population.

Farms for products such as palm oil are other examples of agri-business ventures which might seem benign as they involve the use of plants, but this industry still has a detrimental impact on the biodiversity of our flora. Plants don’t have mouths to speak, to tell us about the damage we’re doing to them and the planet at large. However, what we can see is how the climate changes when plants are absent from the equation. As we wrote recently, by planting more trees on old farmland, it’s estimated we could boost rainfall in Europe, suggesting that where there’s more greenery, there’s more water.

Plants are special organisms which do the seemingly impossible task of turning sunlight into food, but they also become food in time, as well as serving as effective methods to capture carbon. Plants have existed on Earth long before humans, and animals are locked in this symbiotic bond with them. We exchange the gases the other needs to breathe, and just as plants provide nutrition for us to survive in food terms, so too do our bodies, when they are broken back down into soil after death. It’s a life cycle that mutually benefits both parties, and so long as we keep up our side of the bargain, plants will continue to keep up theirs.

Plants come in all shapes and sizes, and are integral in our lives, from the paper we use in writing to the foodstuffs and substances we ingest to maintain good health. Not only do they serve our immediate needs, but they also play a role in the health of our planet as well, maintaining the hydrological cycle and keeping a lid on temperatures wherever they grow. With initiatives like the Great Green Wall springing up in Africa, the age of plants has just begun, and with our help, they can continue to thrive alongside us.

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