Garden Displays Ltd

This chapter introduces the first unavoidable references to percentages, estimated numbers, and scientific hypotheses. Current scientific evidence suggests that over 99% of all species that have ever lived—plants, animals, fungi, and microorganisms—are now extinct. Estimates indicate that there are currently between 10 and 14 million species living on Earth, of which only around 1.2 million have been formally identified and described.

In addition, a 2016 study proposed that there may be up to one trillion microbial species still undiscovered. Most unidentified organisms are microscopic invertebrates or poorly studied life forms living in habitats that remain largely unexplored, such as remote rainforest canopies, deep ocean floors, and underground ecosystems. It is also estimated that around 10,000 new invertebrate species are identified and named each year. Even without the continual discovery of new species, it would take hundreds of years to identify and describe all existing invertebrate life on Earth.

 
Biodiversity loss and human influence
Extinction driven by human activity is accelerating at an unprecedented rate. Land-use change—particularly deforestation for large-scale food production—over-exploitation of natural resources such as fishing, pollution, and other human-led pressures are all contributing to climate change and the rapid loss of biodiversity.

Estimates of decline are often debated, with some studies presenting more alarming figures than others. However, regardless of the exact numbers or percentages, the overall trend is clear: biodiversity loss is severe and ongoing.

 
A shared origin of life
Despite the vast diversity of life, both extant and extinct organisms share fundamental similarities. Many scientists believe this points to a common origin of life, linking all plants, animals, fungi, and microorganisms to a single—or very small number of—ancestor(s). This idea is known as the Last Universal Common Ancestor (LUCA) hypothesis.

This concept can be visualised through a phylogenetic tree, or tree of life, which biologists use to illustrate evolutionary relationships among all living organisms. If we trace our own lineage backwards—from ourselves, to our parents, grandparents, and beyond—continuing further back through evolutionary time, diversity gradually diminishes until we reach the point at which life first emerged. From that origin, all life branches outward. The LUCA hypothesis will be explored further later in this book.

 
The overlooked majority of life
For many people, wildlife-friendly or eco-conscious gardening focuses primarily on visible and often attractive species such as bees, butterflies, birds, and mammals like hedgehogs. While these organisms are important, far less attention is given to the vast and largely unseen world of decomposers and detritivores.

These organisms—mainly bacteria, fungi, nematodes, arthropods, and other soil-dwelling life—are believed to account for around 70% of global biomass. They are the foundation of healthy ecosystems. Without them, nutrient cycling would cease, soils would become sterile, and ecosystems—including our gardens—would collapse.

Although most of these organisms are invisible to the naked eye, their presence is constantly evident through the processes they drive: decomposition, soil formation, and nutrient availability. Their ecological importance deserves the same recognition as birds, bees, and butterflies.

 
What this means for our gardens
Many traditional gardening practices—such as the use of herbicides, pesticides, fungicides, and synthetic fertilisers—negatively affect these vital organisms. Yet despite this pressure, biodiversity often shows remarkable resilience. In gardens especially, life frequently recovers or persists in reduced but functional forms.

This resilience is most clearly seen each year in the natural breakdown of organic matter: fallen leaves, plant debris, and dead animals are steadily decomposed and returned to the soil. This process, largely carried out by microscopic and soil-dwelling organisms, underpins everything else that grows and lives above ground.

Understanding and respecting this hidden majority of life is fundamental to eco-conscious gardening. When we garden with soil life in mind, we support not only wildlife but the very processes that sustain all life in our gardens.