Biodiversity, from ocean and forest to city

Abstract

Today's major environmental issues are energy, water, climate change and biodiversity.

Biodiversity was born in the ancestral ocean, built on pre-biotic chemistry derived from earlier geo-diversity, around 3850 million years ago (Ma), when the first cells cloned by scissiparity. Life then diversified in the ocean over billions and hundreds of millions of years, and essential events took place: the emergence of the eukaryotic cell, the capture of bacteria that would become organelles through symbiosis (mitochondria and plastids), multicellularity and, finally, the development of sexuality. Everything was in place when organized metazoan life emerged from the oceans around 450 Ma. Biodiversity (arthropods) exploded on the continents in the Carboniferous forests and spread everywhere, with species organizing themselves into populations, ecosystems, biomes... Since 570 Ma, some sixty "extinction crises" have been recorded, including five particularly significant ones, the most acute of which took place around 251 Ma, between Permian and Triassic (Paleozoic/Mesozoic hinge), during which 96% of the major species became extinct.

Biodiversity is much more than the species catalogs and inventories that have been compiled over the last few centuries, on the basis of major expeditions or long periods of fieldwork. Biodiversity is, in fact, all the relationships established between living beings and their environment. Quite simply, it's the living part of nature!
Biodiversity is currently threatened by four major phenomena in which mankind plays its part: the destruction and contamination of natural environments, excessive predation and over-exploitation of natural resources, the uncontrolled introduction of species from one environment to another and, last but not least, global warming. After the conquest of fire (around 800,000 years ago), the end of nomadism in the Neolithic period (12-8,000 years ago), the development of agriculture and livestock breeding and, later, the invention of the steam engine (late 18th ^century), humans have had an ever-increasing impact on natural environments, profoundly transforming them. In reality, today we are simply prolonging and accelerating this movement, amplified by demographics and the deleterious idea of nature's "enslavement". In three-four centuries, humanity will have exhausted all the fossil fuel resources accumulated over hundreds of millions of years and, today, living species are disappearing from the planet at a rate 100 to 300 times higher than the expected "natural" extinction rate. This has led some to wonder whether humans are setting the stage for a sixth mass extinction crisis! We are faced with increasingly accurate forecasts of finite resource depletion in our finite world. Only living resources are renewable, but humans often overexploit them, exceeding the "thresholds of renewability".

The richest ecosystems in terms of species are, on the continents, the tropical rainforests and, in the oceans, the coral reefs. Today, we know of just over two million species (1.7 million terrestrial and 300,000 marine), described and deposited in museums. Over 80% remain to be discovered.

Since 2007, the majority of humanity has been living in cities, and we are now particularly interested in the return of biodiversity to the city. Why is it imperative to halt this erosion of biological diversity? Quite simply because we can't do without it - we're made up of it, and we're constantly living alongside it! The services it provides are inescapable. In 2002, in Johannesburg, the United Nations set the year 2010 as the target for halting this erosion. However, at the introductory conference for the year dedicated to biodiversity at Unesco in Paris in January 2010, we collectively realized that we had failed. We then decided to push back the deadline to 2020 and dedicate the decade 2010-2020 to saving biodiversity. But why should we be more successful between 2010 and 2020 than we were between 2002 and 2010? A realistic project or a fool's dream? This is a question we asked ourselves at the Collège de France's first colloquium abroad, in Brussels in 2006. In this context, the contribution of participatory science is very substantial, both in terms of supplying data to researchers who cannot be present everywhere, all the time, and in terms of making the general public and "amateurs" aware of their responsibilities and, collectively, putting pressure on those involved in unsustainable development.

Through the changes of all kinds that it has unleashed over the last two centuries, and which are accelerating, mankind is certainly creating favourable conditions for the appearance of new species, but in the process it is also destroying ecosystems. The result is likely to be dismaying. Humans, with their range of activities, plants and domesticated animals, have become the most powerful evolutionary force exerted on nature. We have entered the Anthropocene. We are reflecting on the limits of adaptability of both ecosystems and humans. Can we simply adapt to ourselves? Natural capital cannot be depleted indefinitely, and we cannot do without the services provided by ecosystems. By estimating evolutionary speeds, trying to predict possible trajectories and planning mechanisms in advance, we could undoubtedly greatly reduce our impact on species and ecosystems, and seriously improve the economic and social costs of our activities on nature. Widespread awareness is underway, but will the pace of change in our habits be at least as fast as that of the environmental changes of all kinds that we are triggering around us? We can't be sure. In the course of the ^21st century, will we be able to fully justify, and at last merit, the term sapiens with which we have labelled ourselves?