Banaue Rice Terraces of Luzon, Philippines
Banaue Rice Terraces of Luzon, Philippines. Photo: © Ori (CC BY-SA 3.0)

10 Reasons Why Plants are Important

In this article we take a look at the unique value of plants and show how all living creatures are dependent upon the benefits they offer.

The thing that makes Planet Earth so different from other planets, is its unique ability to sustain life. Only Earth has a biosphere, and it’s filled with an extraordinary variety of animals, birds and fish.

Yet, as we shall see, without plants (by which we mean trees, shrubs, grasses and all other vegetation, as well as ocean phytoplankton), none of this wonderful biodiversity would exist. Because without them there would be no food and no oxygen. So all animals, birds, fish and humans would die. This is why plants are important and why we should protect them wherever possible.

As our climate crisis gets worse, plants are becoming even more important. Several countries are developing new climate change adaptation policies involving ‘sponge cities‘. These are urban areas in which plants and vegetation are used to absorb increased rainfall and flood waters. The development of more heat-resistant plants is another essential strategy to combat rising temperatures around the world.

Plant Species

There are currently over 400,000 species of plants on Earth 1 divided between two types of seed plants. These are: “angiosperms” (who produce flowers in order to reproduce), such as grasses, asters, begonias, lavender, lilies, magnolias, orchids, roses, tomatoes and tulips; and a much smaller group of “gymnosperms” (who don’t), such as pine, spruce, fir and related species.

There is also a third group of plants who differ from seed plants as they reproduce by means of spores rather than flowers and seeds. Examples include ferns, lycophytes and mosses.

Plant Evolution & Anatomy

Most plants moved from the ocean to land around 470-500 million years ago, at roughly the same time as phytoplankton became active photosynthesizers. 2 3 As a result, plants were forced to make significant changes to their biological structure and behaviors, in order to survive. For example, they developed three different parts of their anatomy: leaves, roots and stems.

(a) Leaves, aided by their green pigment known as chlorophyll, focus on photosynthesis – producing the food that gives the plant the energy to grow – as well as on the related activities of respiration and transpiration. (b) Roots absorb water and nutrients from the surrounding soil, anchor the plant and often act as a store of food. In the case of certain plants, like mangroves, the roots also act as an additional breathing system when the plant is underwater. It is not uncommon for 40 percent or more of a plant’s mass to be tied up in an underground root system. (c) Stems (including shoots and branches) carry nutrients from the roots to the leaves. They also shape the size and height of the plant, which in turn determines how much sunlight they receive. 4

How Plants Adapt

One of the best examples of how plants adapt to hostile environments are mangroves – a species of trees or shrubs found along the shorelines of coasts, rivers, and estuaries, in the tropics and subtropics.

Mangroves live in salty water, with a low oxygen content and limited access to freshwater. They solve the salt problem by filtering and excreting salt. They solve the oxygen problem by growing aerial roots, with thousands of tiny breathing pores, as well as pencil-like cone roots (pneumatophores) that stick up out of the muddy ground like snorkels, to suck in oxygen from the air.

Finally, they overcome the lack of freshwater the way that desert plants do – by conserving fresh water in thick succulent leaves, whose waxy coating minimizes evaporation. Small hairs on the leaves also help to deflect wind and sunlight, which can increase the loss of water through the tiny openings (stomata) used for photosynthesis.

Plant Science

The scientific study of plants is called botany. Human cultivation of plants is a branch of agriculture. The science and aesthetics of plants is called horticulture. The science and study of wooded plants (trees, shrubs, and lianas) is called dendrology. The study of forests and woods is known as silvology. The science and practice of planting, managing, and caring for forests is called forestry.

10 Reasons Why Plants Are Important

This is not a comprehensive list of the benefits offered by plants, just a selection of the most useful in today’s warming world.

1. Plants Create Food Energy For the Whole World

Plants create their own food energy by a process known as photosynthesis – a process unique to the plant kingdom. They draw water from their roots, absorb carbon dioxide from the air and combine both with sunlight to produce complex carbon-containing molecules. Ocean phytoplankton perform the same task for the marine world.

All carbon in fats, proteins and carbohydrates can be traced back to photosynthesis in plants. Everything we eat, including meat from animals (which feed on plants) derives from the unique ability of plants to make use of the energy in sunlight.

Plants and phytoplankton are known as “autotrophs” – meaning, they do not depend upon a living source of food energy. Instead, they can create food energy from non-living material, such as water, air, soil, sunlight or minerals. “Heterotrophs”, by comparison, cannot create energy from non-living material. Almost every living creature except plants and phytoplankton is heterotrophic.

So, in a nutshell: plants (autotrophs) create food energy from sunlight and store it in their tissues. As they are eaten by other creatures (heterotrophs) the energy is transferred up the terrestrial food web for the benefit of all living beings, including us. The marine food web works in the same way. The point is, without plants and phytoplankton, virtually no other living creature could survive.

Human Agriculture Based on Plants
The establishment of settled communities based on farming and agriculture around 10,000 BC, marked the first real growth in the human population. Since then, humans have continued to depend on plants for food, either directly or as feedstock for livestock and agriculture (the production of food crops) has played a key role in our civilization.
Roughly 7,000 species of plants have been used for food, although most of today’s food comes from only 30 species. Staple foods include cereals, such as rice and wheat; starchy root vegetables like potatoes; legumes, like peas and soybeans, and more.

2. Plants Produce the World’s Oxygen

Photosynthesis involves a number of chemical reactions. One of them causes plants and phytoplankton to release oxygen into the atmosphere – oxygen that makes the planet habitable for humans and every other living species.

Half of the world’s oxygen is produced in the ocean by phytoplankton. The other half is produced on land by trees, grasses, shrubs, and other types of plant vegetation. 5

True, the air we breathe contains three times more nitrogen (78 percent) than oxygen (21 percent), but it’s oxygen (O2) that’s vital for our cells. Without the oxygen that is continually pumped into the air by these simple-but-incredible plants and phytoplankton, few if any life forms could survive for long.

Historically, this release of oxygen helped to convert Earth from a hostile, uninhabitable environment into the ultimate Goldilocks biosphere. It happened like this. As plants started to photosynthesize, the atmosphere began gradually to fill up with oxygen, some of which was converted to ozone (O3) in the stratosphere. After a while there was sufficient ozone in the upper atmosphere to form a protective filter against the highly damaging ultraviolet rays from the sun. This filter allowed living creatures to survive on land and in the surface waters of the ocean.

Today, however, the planet’s oxygen producers (phytoplankton and plants) are coming under pressure from rising temperatures. For more on this, please see: 7 Effects of Climate Change on Plants.

3. Plants Boost the Water Cycle

Water signifies life. That’s why astronomists searching for extra-terrestrial life look for signs of water. Well plants play a key role in Earth’s water cycle by distributing and purifying the water supply.

For example, through the process of transpiration, plants in the Amazon Rainforest and the Congo Rainforest draw water up from the soil via their roots, and release it back out into the atmosphere via their leaves. This moisture evaporates in the heat and the vapor rises up into the air, eventually condensing into liquid droplets and forming clouds, before returning to Earth as rain to revitalize the soil and the whole environment. This is why rainforests are famous for creating their own mini weather system. 6

4. Plants Help to Create Habitats for Other Organisms

Plants constitute the bulk of Earth’s landscape, providing edible foliage and vegetation, water, homes, and shelter for countless ants, beetles, worms, small mammals, reptiles, large mammals and birds. Without these boreal forests, grasslands, rainforests, savannas, or wetlands, many animals and birds wouldn’t survive.

If you read any of our articles on animals and birds, such as 10 Endangered Animals, or 10 Birds Threatened by Climate Change, or Endangered Birds of Prey, you can’t help but appreciate the crucial link between habitat and survival.

Plants provide materials for nests, cover for dens and lairs, hollows for homes, rotting debris for insects, as well as tree perches for tropical grassland mammals like leopards and numerous birds of prey. All of the world’s biomes that are noted for the diversity of their animals have a rich variety of plant life.

Harbor seal in kelp forest, California coast. Kelp is one of the most useful marine plants
Harbor seal (Phoca vitulina) in kelp forest off the coast of California. Photo: © Kyle McBurnie/ Smithsonian Institute.

In the ocean, forests of kelp and seaweed are invaluable habitats for small invertebrates like bristle worms, scud, prawn, snails, brittle stars, sea stars, anemones, crabs, and jellyfish. Fish include species such as blue rockfish, olive rockfish, black rockfish, and kelp rockfish. Sea lions and seals prey on the fish that inhabit kelp forests, as do sea otters and grey whales.

Kelp forests are also a draw for birds like crows, black phoebes, starlings and warblers, which feed on flies, maggots, and other insects. Meantime, a wide range of cormorants, egrets, gulls, herons, and terns feed on the many fish and crustaceans living in the kelp.

Unfortunately, the effects of global warming on oceans are killing off kelp forests through higher water temperatures, which have also indirectly led to an explosion in the population of long-spine sea urchins, a species that destroys sea-floor vegetation. 7

5. Plants Play a Vital Role in the Carbon Cycle

Plants are vital to the carbon cycle because they serve as a natural carbon sink capturing carbon dioxide (CO2) from the air whenever they photosynthesize. They also emit CO2 during respiration, but nothing like the amount they capture during photosynthesis. The fast carbon cycle relies heavily on plants to absorb carbon from the atmosphere and make it available either to the soil, or to animals and other organisms. For more on this, see: Is more CO2 good for plants?

Most importantly, trees absorb much of the carbon dioxide emitted during the burning of fossils fuels which would otherwise fuel the greenhouse effect causing temperatures to rise around the globe. In reality, plants are the perfect natural carbon capture and storage system. (See also: Which is the Largest Carbon Reservoir?) When carbon dioxide is released into the atmosphere from fossil fuel combustion, roughly half stays in the atmosphere, while one quarter is absorbed by land plants and trees, and the other quarter goes into the ocean. 8

Sadly, deforestation releases this stored carbon into the atmosphere, boosting global warming and destroying precious forest habitats. This is why wood burning is so bad and tree-planting so much more preferable.

Phytoplankton, too, absorb CO2 as they photosynthesize, much of which is recycled in the upper ocean by marine microbes who drive the food web, with only a fraction reaching the ocean floor and becoming lithified in the slow carbon cycle.

There’s another set of plants that scientists are beginning to realize are even more important than rainforests, when it comes to sequestering CO2. They are coastal marine plants, like seagrasses, kelp forests and mangroves, which are renowned for their efficient storage of so-called “blue carbon” – that’s carbon absorbed by ocean plants and stored underwater.

6. Plants Help Soil

Trees, plants and shrubs are vitally important for healthy soil for several reasons. Their roots and the microorganisms that live around them hold the soil together, reducing soil erosion. And when leaves or plants die and sink into the forest floor, they are broken down by decomposers into their chemical components, which then fertilize the soil.

Plants (such as certain clovers, peas and beans) help to fix nitrogen in the soil, while also preventing the soil from drying out. Plants also provide the soil with nutrition. Comfrey, for example, accumulates a lot of nutrients, and its leaves are so fertile that they are often compared to manure. For more, see: Why is Soil So Important to the Planet?

7. Plants Help to Reduce Air Pollution

Plants and trees reduce air pollution by absorbing pollutants. 9 In particular, evergreen conifers, like pines and cypresses, are good for the dispersion and deposition of tiny aerosols and other particulate matter (PM). In fact, any tree with rough, hairy surfaces is a good filter for PM.

In a recent study, silver birch, yew and elder trees proved to be the most effective at capturing particles, including black carbon, and it was mostly due to the hairs on their leaves that enabled them to attain PM reduction rates of 79 percent, 71 percent and 70 percent respectively. Nettles, by comparison, captured a smaller but still respectable 32 percent. 10

Overall, conifers, evergreen oaks, and common yew are regarded as potentially most effective. They are evergreen, relatively tolerant of air pollution, and have several beneficial leaf traits.

8. Plants Provide Important Products

What would the world be like without rubber tyres, timber, cotton clothes, dyes, paper, shampoo, cosmetics and the thousands of other products that come from plants? And what about all those fossil fuels that come from buried plants? Sure, we now understand that they cause global warming and must be phased out, but imagine a world without cars or trucks: a world in which everything had to be transported by horse and cart, or barge.

Imagine a world without machinery, a world in which slave labor was still needed for large construction projects because there were no machines to move heavy loads. Because most of these machines are made from steel (forged using plant power) or plastic (made from plants), and run on diesel or some other fossil fuel (also made from plants). The same could be said about computers and mobile phones.

The reason why we can now contemplate the creation of a ‘green’ world is because of the technological progress we have achieved, thanks to plants.

9. Plants Provide a Variety of Medicines

Thousands of medicines are either made from plants, or from chemical substances first obtained from plants and then synthesised for use in modern medicine.

Medicinal drugs derived from plants include aspirin, morphine, the anti-cancer drugs taxol and vincristine, the anti-malaria ingredient quinine, the hypertension drug reserpine, the heart drug digitalis, alkaloid d-tubocurarine, used to treat Parkinson’s disease and multiple sclerosis; and many more. The United States National Cancer Institute has identified 3,000 plants from the rainforest alone, as having potential anti-cancer properties.

According to the World Health Organization, around 65-80 percent of the world’s population use plant-based medicine for their primary health care needs. In addition, a wide array of plants is used in herbal medicine, such as echinacea, feverfew, ginkgo, and Saint John’s wort. Another good reason to reduce deforestation in Southeast Asia and in the Congo Rainforest, as well as the Amazon Basin.

Today, more than 100 pharmaceutical companies, including multinational corporations like Bayer, GlaxoSmithKline, Johnson & Johnson, Merck, Monsanto, Pfizer, Roche and others, are engaged in plant-based projects in the tropical rainforest ecosystem to find botanicals to treat infections, AIDS and cancer.

10. Plants Help to Combat the Effects of Climate Change

In addition to capturing carbon dioxide from the atmosphere (point 5, above), plants are becoming an important resource in reducing the effects of global warming in a variety of settings. It’s all part of the new climate-proof approach to urban planning known as green infrastructure, which is based on the idea of building with nature to create a more habitable environment. 11

Why Do Cities Need Trees?

A recent report published by the Greater Sydney Commission, in Australia, singles out urban heat as one of four high priority areas to cope with global temperature projections over the next few decades. The report identifies the improvement of tree canopy as the most effective response. 12

Other city authorities seem to agree. For example, cities as far apart as Athens, Adelaide, New York, Milan, Melbourne, Seoul, and Toronto (among others), are planting trees to obtain a variety of climatic benefits.

Trees are a highly effective method of improving a city’s microclimate. Their leaves absorb much of the sun’s radiation, providing shade, while also cooling the surrounding air through transpiration of water vapor from their leaves. In addition, trees and urban greenspace help to absorb sudden downpours and prevent flash flooding through rainfall interception and percolation. By comparison, areas of concrete and asphalt are several degrees hotter. See also: Tree Planting: The Answer to Global Warming?

A "Sponge City" project in Jinhua City, China. Making full use of plants to offset global warming
The Yanweizhou Park sponge-city project, Jinhua City, in the Yangtze River Delta, China. Sponge cities are designed to minimize the effects of climate change by absorbing and reusing flood water. Credit: Turenscape

Sponge Cities

A ‘sponge city’ is designed to capture rain water and then utilize it to reduce floods. The water can be redirected for irrigation and home use. A sponge city is like a sustainable drainage system but on a much larger scale. According to Kongjian Yu, Dean of Peking University’s College of Architecture and Landscape Architecture – instead of funnelling rainwater away, a sponge city retains it for its own use, within its own boundaries. 13

Instead of using stone and concrete to channel rainwater into already-full drains, the “sponge city” absorbs the excess rainwater for its own uses. Such uses might include: irrigating gardens and urban farmland, refilling depleted aquifers, replenishing the water used to flush toilets, and processing it so that it can be clean enough to use as drinking water, and so on.

The sponge city concept has been taken up by several countries, including China – a country where urban flooding has doubled in recent years – where the government has introduced pilot projects in 16 different districts. 14

Green Roofs

Green roofs are another relatively new technique used in the construction of climate-proof buildings. Available in three basic formats: extensive, semi-extensive and intensive, with soil depths of between 5 and 30 centimetres (12 inches) – they are designed to mitigate climate change by reducing run-off from increased rainfall. Studies have shown that green roofs are able to intercept 50 percent of annual rainfall, while roof gardens with deeper soils can intercept up to 90 percent. 15

Apartment block with roof garden containing plants, shrubs, trees and grasses
A green roof is just a roof which is planted with a variety of green plants, grasses and shrubs in order to reduce water runoff, prevent combined rainwater/sewer water overflow, neutralize the acid rain effect and absorb nitrogen pollution from the rainwater. Photo: © ZinCo International Green Roof Systems.

Green Infrastructure: Coasts, Waterways

Developing mangrove forests (mangals) is another way of adding to green infrastructure along coasts and estuarine waterways. Mangroves are able to bear the brunt of storm surges and other extreme weather events that affect coastlines, thereby minimizing damage to homes and agriculture. They restrain coastal erosion, and stabilize the coastline in the process.

Like coral reefs, mangals offer food and shelter to a variety of marine animals, thus helping to stem the loss of biodiversity from both global warming and other human activities.

In addition, as we saw, mangrove forests are famous for their storage of “blue carbon” – that is, carbon dioxide absorbed from the air and stored underwater – which adds even more to their value as an important item of green infrastructure.

Recife Urban Mangroves
The city of Recife, Brazil, in the northeast corner of South America, boasts the largest urban mangrove forest in the world. Photo: © Portal da Copa/ME (CC BY 3.0)

References

  1. State of the World’s Plants.” Royal Botanic Gardens, Kew. []
  2. Earliest land plants created modern levels of atmospheric oxygen.” Timothy M. Lenton, et al. PNAS August 30, 2016 113 (35) 9704-9709. []
  3. Pulse of atmospheric oxygen during the late Cambrian.” Matthew R. Saltzman, et al. PNAS March 8, 2011 108 (10) 3876-3881. []
  4. Introduction to Plants.[]
  5. Source of Half Earth’s Oxygen Gets Little Credit.[]
  6. Transpiration.[]
  7. As Oceans Warm, the World’s Kelp Forests Begin to Disappear.[]
  8. Ocean-Atmosphere CO2 Exchange.[]
  9. The best trees to reduce air pollution.[]
  10. “Efficient Removal of Ultrafine Particles from Diesel Exhaust by Selected Tree Species: Implications for Roadside Planting for Improving the Quality of Urban Air.” Huixia Wang, et al. Environ. Sci. Technol. 2019, 53, 12, 6906–6916. 2019. https://doi.org/10.1021/acs.est.8b06629 []
  11. What is Green Infrastructure?[]
  12. Performance Indicator: Addressing urban heat.[]
  13. Sponge Cities: What is it all about?” World Future Council. []
  14. China’s ‘sponge cities’ aim to re-use 70% of rainwater – here’s how.[]
  15. Could green roofs offer a solution to urban environmental challenges?[]
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