How many different species live on this planet?
You would think this would be an easy question to answer. After all, we have been giving plants and animals names since before recorded history. And for the past couple of hundreds of years biologists and other scientists have been hard at it trying to classify everything under the sun.
But it is one of the most difficult questions in biology as there are so many species undiscovered. Just last year, 270 new species of animals and plants were described.
We are constantly finding new creatures in places such as deep in the ocean, in steep ravines above raging rivers, caves underground, and the dense tropical forests.
Most new creatures are small in size - for example, 120 new species of wasp and 28 new species of ants - but a few are larger such as the Dinizia jueirana-facao tree which can be 130 feet tall and weigh in at 62 tonnes. There are only 25 individuals of this species of tree known marking it as endangered as well as newly discovered.
We are constantly adding to the list of life on the planet and many scientists argue we have barely scratched the surface because we have primarily focused on eukaryotic organisms. These are species with cells having their nucleus and other organelles enclosed by a membrane such as animals and plants. The other major branches of life are the prokaryotes and archaea which lack membrane-bound organelles but easily outnumber the eukaryotes.
While estimates of the total number vary, a 2011 report put the number at 8.7 million plus or minus 1.3 million eukaryotic species on the planet. A 2016 study went a little further and included all forms of life. Based on the total biomass, the authors concluded there are more than one trillion genetically distinct species on Earth with the vast majority being microbial and undescribed.
Furthermore, it has been estimated that 99 per cent of all the species which have occupied the Earth are now extinct.
Everything from the towering dinosaurs to stromatolites to trilobites to giant ground sloths have come and gone from the face of the planet.
Extinction is the way of life on Earth and it would be foolhardy to think we are immune to these massive forces.
Indeed, we seem to be doing our best to hurry up the process. A new report released by the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) warns us that one million species of plants and animals face extinction, many within the next few decades, as a result of human activities.
The report distills the findings from approximately 15,000 scientific reports, integrating information from a wide variety of sources, including Indigenous people and traditional agricultural communities.
Representatives from 132 governments met in Paris last week to finalize and approve the document ahead of the UN Convention on Biodiversity next year.
The report is not all about climate change although it does recognize climate change as a contributing factor. Changing climatic conditions stress both animal and plant life, disrupting the food web and diminishing biodiversity.
However, the report mainly focuses on human activities such as agriculture, deforestation, and overfishing which are leading to species loss. About 75 per cent of the land and 66 per cent of the oceans have been significantly altered by human impact driven, in large part, by agriculture and aquatic activities. Crops and livestock presently occupy more than 33 per cent of the land surface and consume 75 per cent of the world's freshwater supply.
Put another way, the world's population of lions is now about 40,000 compared to the 600 million house cats while the 900,000 wild African buffalo are vastly outnumbered by the 1.5 billion domesticated cattle or the 20 billion chickens. Wildlife populations are imperiled and estimated to have halved since 1970 while domesticated animals are taking over the landscape.
While extinction of lions or African buffalo might not have happened yet, the drastic decrease in wild populations are putting an increasing number of species at risk.
All of this puts the world's biodiversity under threat. Many scholars are now describing the present as the Anthropocene epoch - the time of humanity. We have become the single most dominant force for global ecological change and we are not necessarily a force for good.
The IPBES report makes it clear we face an existential dilemma. While life will go on long past our time, we are heading toward a crisis. Without transformative changes to our approach to agriculture, economics, social and political systems, major biodiversity loss will continue and potentially accelerate during the latter part of this century.
Mass extinction of life on this planet has happened five times that we know about. The geological record contains an unequivocal record each time life has approached the brink. Life has always found a way to rebound. But not all species survive.