We humans have a complex relationship with the other inhabitants of Earth. We are the dominant animals on the planet while making up only .01 percent of living things. We are the primary users – and wasters – of the earth’s resources and the predators at the top of the food chain, consuming plants, and other animals.
Plants can live without humans, but humans cannot live without plants.
As the earth was formed, first came bacteria, fungi, and other single cell organisms, including algae, followed by plants which emerged and evolved on the planet long before humans and other animals appeared. Plants and algae created the oxygen-rich atmosphere which allows us to exist.
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While algae are plant-like, since they contain chlorophyll which captures light energy for photosynthesis, they are not plants, nor fungi, nor even bacteria. Most algae are microbes which live in the sea and other bodies of water.
Scientists estimate 50 percent to 80 percent of the earth’s oxygen is produced by algae and drifting plants in the ocean, but much of this is used by ocean animals. Many things negatively impact the amount of oxygen produced by algae, including ocean circulation patterns affected by climate change, water temperature, and increased nutrients from human activity.
Trees supply oxygen, clean the air
As the largest plants, trees are essential to human survival. They supply oxygen, food, and shelter; help clean the air we breathe; filter the water we drink; and provide habitat to over 80 percent of the rest of earth’s inhabitants.
The sun is the original source of most of the energy on Earth. Humans can only access this vital source of energy for use by their bodies indirectly with the help of plants. Plants consumed as food provide chemical energy, which has been converted by plants from the sun's light energy through photosynthesis.
Photosynthesis only occurs in plants, algae, and some bacteria. Through photosynthesis, the sun's energy is absorbed and creates a chemical reaction with carbon dioxide and water, forming glucose, C6H12O6, a type of sugar, and emitting oxygen.
You get access to the sun’s energy by breathing oxygen and by eating plants, or third hand from animals which have fed on plants.
Plants, glucose and metabolism
Chemically, we are not all that different from trees. All life on earth is composed of a few major elements. Ninety-nine percent of our bodies are composed of oxygen, hydrogen, nitrogen, carbon, and phosphorus, with trace elements making up the other one percent.
Plants consist mainly of carbon, hydrogen, and oxygen, with five percent of other chemicals. Microorganisms are composed of carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur, with 10 percent trace minerals.
The glucose created by plants through photosynthesisis used to produce roots, leaves, wood, and fruit, and to sustain the microorganisms necessary for plant growth. This is the exact same glucose which plays a vital role in your body’s metabolism.
Most of the cells in your body need glucose. Glucose (blood sugar) is the primary source of energy for your body. It is produced by your digestive system, mainly from carbohydrates – sugar molecules – in the plants you eat.
It provides energy to your cells and keeps your body functioning properly. It's the main source of fuel for your brain. Nerve cells and chemical messengers there need it to help them process information. When your brain doesn’t have enough glucose (low blood sugar), it can’t communicate with the rest of the body as well and the body’s functions start to degrade.
Fungi, microbes and carbon dioxide
We also depend for life on fungi, bacteria, and other microorganisms – they are the facilitators, the fixers, the decomposers. These tiny organisms obtain nutrients and energy by establishing close relationships with other living things, including symbiotic, mutualistic, and parasitic relationships. In return they provide services to plants and animals, including humans.
Ongoing research indicates that, among many other services, microbes in your body help convert your food to a form available as nutrition, help to regulate your metabolism, and influence your immune system and the development of disease. Microbes also provide these and many other essential services for the plants which sustain us.
We are mostly unaware of the microbes which are necessary for life, and we tend to take plants for granted. We pollute much of the earth’s water and eliminate trees and other plants in the process of human development, or for aesthetic purposes, but we exist because of our symbiotic relationship with them.
We require the oxygen and food they produce, and they utilize the carbon dioxide that we exhale, or human civilization creates.
The current excess of carbon dioxide in the atmosphere is caused by human production of more carbon dioxide than the existing trees, plants, and algae can utilize or store.
Trees are particularly good at storing carbon in the soil, yet we continue to destroy them to make way for more carbon dioxide producing processes.
Dependent on plants
In summary, we are totally dependent on plants and algae for our existence because they are the only producers of oxygen on the planet.
In addition, we are created from plants because everything we eat is either produced by a plant or is from an animal which has eaten a plant. The food we eat is produced and made available to our bodies only with the help of fungi and other microorganisms.
Nature is not something which can be considered apart from humanity. It is our life support system, and we are the primary factor in its degradation and change going on at an exponential rate.
We simply must treat the other inhabitants of our planet with the respect they deserve and conserve the environments they require to exist for they are keeping us alive.
Janis Piotrowski is a Florida Master Naturalist, a Certified Permaculture Designer, and a Master Gardener Volunteer with UF/IFAS Extension Leon County, an Equal Opportunity Institution. She hosts a blog about gardening and sustainable living in North Florida at https://northfloridavegheadz.blogspot.com. For gardening questions, email the extension office at AskAMasterGardener@ifas.ufl.edu.
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This article originally appeared on Tallahassee Democrat: How plants supply essential ingredients for human life