Ecosystem: What It Is and How It Works in Nature

Imagine taking a photo of the Amazon rainforest from space: an immense green carpet covering millions of square kilometers. Now imagine that each leaf, each insect, each drop of rain, and each fungus in the soil is communicating with all the other elements at the same time, exchanging energy, nutrients, and information in a silent and continuous dance. That is an ecosystem — and it’s precisely this invisible complexity that keeps the planet habitable for us.

The concept may seem technical at first glance, but understanding what an ecosystem is and how it works is perhaps one of the most practical things anyone can do. After all, every decision we make — what we eat, what we wear, how we get around — has some impact on these living systems. And in 2026, with climate change already visible in the daily lives of billions of people, it has never been more urgent to understand the rules of the game.

In this article, we’ll go from the most basic definition to the concrete ways you can help protect the ecosystems around you — even if you live in a large city.

What is an ecosystem: a clear and simple definition

The term ecosystem was coined by British ecologist Arthur Tansley in 1935. He described the concept as a system formed by all living organisms in a given area — plants, animals, fungi, microorganisms — interacting with each other and with the surrounding physical environment: soil, water, air, sunlight, and temperature.

In other words, an ecosystem is a functional unit of nature. It’s not just about the list of species living in a place, but about the relationships between them and between them and the abiotic (non-living) environment.

These systems can vary greatly in scale:

• A mountain lake is an ecosystem
• A temporary puddle is an ecosystem
• The Amazon Rainforest is one of the largest ecosystems on the planet
• A well-balanced home aquarium is a miniature ecosystem

What they all have in common is interdependence: remove one element, and the entire chain suffers consequences. This is precisely why the extinction of a seemingly insignificant species can trigger cascading effects that affect other organisms — including human beings.

How an ecosystem works: energy flow and nutrient cycling

To understand how an ecosystem works, we need to observe two fundamental processes: energy flow and nutrient cycling.

Energy flow in ecosystems

All energy circulating in an ecosystem originally comes from the Sun. Plants (along with algae and cyanobacteria) are the primary producers: they capture solar energy through photosynthesis and transform it into organic matter — leaves, fruits, roots.

This energy then moves through what are called trophic levels:

1. Producers — plants, algae, phytoplankton
2. Primary consumers — herbivores that eat plants (grasshoppers, rabbits, caterpillars)
3. Secondary consumers — animals that eat herbivores (frogs, insect-eating birds)
4. Tertiary consumers — top predators (jaguars, sharks, eagles)
5. Decomposers — fungi and bacteria that break down dead organic matter and release nutrients back into the soil

An essential rule: at each trophic level, about 90% of the energy is lost as heat. This explains why there are far more plants than herbivores, and far more herbivores than large predators.

Nutrient cycling: nature’s recycling system

Unlike energy, which flows in one direction and dissipates, nutrients are continuously recycled. Carbon, nitrogen, phosphorus, sulfur — all circulate between living organisms and the physical environment in biogeochemical cycles.

Decomposers are the great heroes of this process. When a leaf falls on the forest floor, fungi and bacteria transform it into humus, releasing nutrients that will feed new plants. It’s a closed system of reuse that has been working for hundreds of millions of years — and that any home composting garden imitates on a smaller scale.

Types of ecosystems around the world and in Brazil

Ecosystems can be grouped into large categories called biomes. Brazil, due to its size and geographic diversity, is home to some of the richest biomes on the planet:

Each of these biomes hosts specific ecosystems with unique species, many of which have not yet been cataloged by science.

Why ecosystems are essential for human life

Here’s something many people still don’t fully grasp: we cannot survive without healthy ecosystems. And it’s not just an aesthetic or sentimental matter.

Ecosystems provide what science calls ecosystem services — concrete benefits that nature offers for free and that sustain human civilization:

• Climate regulation: forests absorb CO₂ and regulate regional temperature and humidity
• Water purification: riparian forests and wetlands naturally filter river water
• Food production: pollinators like bees and butterflies are essential for agriculture
• Pest control: natural predators keep insect populations in balance
• Disaster protection: mangroves and coastal forests reduce the impact of storms and floods
• Medicines: a large portion of modern pharmaceuticals originate from compounds found in plants and organisms from natural ecosystems

The IPCC and the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) systematically warn that the degradation of these services represents one of the greatest economic and social risks of the 21st century — not just environmental.

What threatens ecosystems today

In 2026, pressures on global ecosystems remain intense. The main threats identified by the scientific community include:

• Habitat destruction and fragmentation: conversion of forests and savannas into agricultural or urban areas
• Climate change: alterations in temperatures, rainfall patterns, and frequency of extreme events that disrupt biological cycles
• Invasive species: animals and plants introduced into ecosystems where they did not evolve can devastate native populations
• Pollution: pesticides, plastics, heavy metals, and excess nutrients (eutrophication) unbalance aquatic and terrestrial ecosystems
• Overexploitation: predatory fishing, illegal hunting, and excessive extraction of natural resources
• Pollinator decline: the global decline of bees and other pollinating insects represents a direct threat to food security

The combination of these pressures creates what scientists call a twin crisis: climate change and biodiversity loss feed each other, making ecosystems increasingly less resilient.

How you can help protect ecosystems in practice

The good news is that individual power matters — especially when combined with that of thousands of other people. Here are concrete actions you can take today:

In daily consumption:

• Reduce meat consumption, especially beef, to decrease pressure on biomes like the Cerrado and the Amazon
• Choose products with sustainable origin certifications (FSC for wood, MSC for seafood, certified organic)
• Avoid food waste — food that goes to waste represents emissions and land use that destroyed ecosystems somewhere
• Think about the impact of fast fashion on water use and ecosystem destruction before buying

At home and in the garden:

• If you have space, plant native species from your region — they attract pollinators and other local organisms
• Set up a home compost bin to mimic nature’s nutrient cycle
• Reduce the use of pesticides and synthetic fertilizers in gardens and vegetable patches
• Save water — pressure on water resources is one of the biggest threats to aquatic ecosystems

In your community:

• Support and participate in cleanup efforts for rivers, beaches, and urban parks
• Get involved with local conservation organizations
• Pressure elected representatives for stricter environmental protection policies
• Educate children about how ecosystems work — awareness starts early

To measure and reduce your impact:

• Calculate your carbon footprint to understand which aspects of your lifestyle have the most impact on climate — and therefore on ecosystems

Conclusion: every action counts in an interconnected system

An ecosystem is, in essence, a network of relationships. And networks are strengthened when each node does its part. Just as a fungus in the forest soil plays an irreplaceable role in nutrient recycling, every person who makes more conscious choices contributes to the resilience of the great ecosystem we share.

You don’t need to change everything at once. Start with what’s possible today: a meal with less meat, a trip to the market with a reusable bag, a conversation about biodiversity with someone close to you. The sum of these small actions is what moves systems — both ecological and social.

The planet has an extraordinary capacity for regeneration when we give it the minimum conditions to do so. Understanding how ecosystems work is the first step toward becoming part of the solution — not the problem. And that step, you’ve already taken.