Why do living beings disappear? A crisis foretold

Climate change, habitat destruction, and pollution put thousands of animals at risk of disappearing. The Earth faces a new mass extinction, but there is still hope for biodiversity conservation.

Throughout Earth’s history, life has never been unchanging. Species appear, adapt, transform and inevitably disappear. This is called biological evolution. Extinction is an integral part of the evolutionary process, but its scale and speed have changed over time. Fossil records show that at least five major mass extinctions have occurred, wiping out huge portions of biodiversity. Today, scientists warn that we are on the verge of the Sixth Great Extinction and, unlike the previous ones, this is not caused by uncontrollable natural forces, but rather by human activity.

The extinctions of the past had different causes. About 445 million years ago, at the transition between the Ordovician and Silurian, a sudden glaciation dramatically lowered the level of the sea and caused the first major biological crisis, with the loss of 85% of species at the time. By the end of the Permian period, 252 million years ago, colossal volcanic eruptions wiped out about 90% of marine and terrestrial life. And 66 million years ago, an asteroid impact in the Gulf of Mexico sealed the fate of non-avian dinosaurs. These episodes demonstrate that rapid weather changes, geological cataclysms and cosmic shocks can completely reconfigure the web of life.

The human impact on biodiversity

Today, however, the engines of extinction are different. The most obvious is habitat destruction. Tropical forests give way to croplands and pastures; coral reefs die due to warming and acidification of the oceans; wetlands are drained for urban expansion. The Javan rhino, today with fewer than a hundred individuals, is one of the direct victims of this loss of territory.

Overexploitation is another crucial factor. Overhunting, along with habitat destruction, led to the disappearance of the dodo, a bird endemic to Mauritius, and the extermination of the passenger pigeon in North America, once one of the most abundant birds on the planet. Species like the pangolin and the bluefin tuna (Thunnus thynnus) currently face similar risks due to hunting and intensive fishing.
Climate change further accelerates this process. Changes in temperature, rainfall and sea level rise force the species to adapt at an almost impossible pace. The polar bear, dependent on sea ice for hunting, sees its habitat disappear year after year. Similarly, coral reefs – true underwater cities of biodiversity – are among the most threatened ecosystems.

Invasive species also play a destructive role. The rabbit introduced to Australia, for example, devastated local ecosystems, contributing to the decline of native marsupials. Plants, insects and microorganisms – larvae (of marine animals), propagules and eggs, often carried in ballast waters of large commercial ships – carried involuntarily by global trade have similar effects in many other territories.

Pollution adds another weight to the scale. Microplastics ingested by seabirds, pesticides that affect bees and butterflies, or oil spills that suffocate fish and marine mammals, make environments toxic and inhospitable.

An open future

Despite the severity of the scenario, there are signs of hope. Human intervention can also reverse trends. The Iberian lynx  case is paramount: considered the most endangered feline in the world in the early 2000s, it is now recovering, and its numbers are increasing thanks to captive breeding programs and the protection of its habitat. This success shows that it is possible to stop extinction when there is political will and scientific cooperation.

The history of life on Earth teaches us that extinction or evolution is inevitable, and diversity can be reborn if we give it time and space. Our main challenge today is deciding whether we want to be the agents of destruction or the agents of preservation. The Sixth Great Extinction is not an inevitable fate; it’s a choice we can still avoid.

On the autumn water route

Trees are absorption and transpiration experts.

Through the roots or with the help of nearby natural rocks, the water molecules that pass through these layers retain only excess bacteria, contaminants or nutrients retained.

Water is absorbed by the roots of trees and plants, and travels through the xylem conductive vessels – a porous tissue on a micrometer scale – through which the crude sap, rich in water, mineral salts and O₂, flows from the roots to the leaves. Water in plants always moves according to the so-called water potential, that is, from where there is more water (soil), to where there is less (atmosphere).

Furthermore, water also dissolves nutrients, especially sugars, generated by photosynthesis, allowing the nutrition of all plant cells through another system of vessels, called phloem.

Different soils also retain and distribute water in different ways.

Let’s look at the example: two different soils with 30% water content, like sand and clay. Sand soil is superficial, and so therefore the level of moisture does not help plant growth due to the poor aeration. Clay, on the other hand, seems to retain and supply water with agility, however, due to its shape and texture, it prevents the passage of essential water levels for the well-being of the plant. What’s more, water always moves from locations with greater potential to lower potential locations.

Later, the tree releases purified water through evapotranspiration, the main process that forms clouds – true regulating managers of global precipitation patterns. At the same time, it creates greater humidity in the air and helps cool the local atmosphere, serving to boost and expand the presence of water on the planet. It is also worth mentioning that the vast majority of water evaporates from exposed surfaces, namely the ocean.

But plant transpiration does not occur during the rainy season alone: a large size oak tree, for example, transpires 151 thousand litres of water per year, about 414 litres of water per day. These data vary and depend not only on the level of moisture in the soil throughout the year, but also on the climate and size of each plant, particularly its leaf surface (number of leaves x leaf area), and the density and size of the stomata.

This natural self-management helps prepare the entire ecosystem for the next rainfall rounds. The process is so thorough that it is able to retain water, prevent flooding and habitat destruction in more fragile spaces, such as plains.

In the event of a flood, water that becomes stagnant on site cannot continue its journey to other areas and spread its nutrients.

Fortunately, tree roots and trunks play a role in soil stability, as is the case with riparian alder groves. These help in the fixation of lands and stabilization of rivers, preventing the movement of mud in slope areas and damages in villages and surrounding lands.

Tight water spots

The problems involving water availability are correlated with human presence and with the way in which it insists on operating negligently on its various fronts of action: whether in spatial planning, urban planning or even in forest management and water resources management.

In addition to availability, water contamination affects biodiversity in ways that are not yet fully understood. The relationship between clean water and healthy living is indisputable, and this delicate balance is vital for the survival of countless species, both aquatic and terrestrial.

For example, in forest areas near urban spaces, household waste, when passing through rainwater currents – untreated water – can reach river areas, where several animals, such as the hedgehog or the red squirrel, insects and humans take advantage of these areas.

These toxic pollutants are harmful to natural habitats: materials and compounds of human nature can kill fish, amphibians and birds. Bacteria, resulting from organic contamination and pollutants, contaminate and create serious diseases in animals and plants. The presence of these objects clouds the waters and hinders the natural progress of life and the growth of new aquatic plants. In fact, this excess of nutrients multiplies the presence of algae – eutrophication – which during decomposition take up too much space and reduce oxygen levels in the water.

This conversion of natural areas into urban and agricultural areas results in the degradation of ecosystems and surrounding biodiversity.

Added to this is climate change, which increases the degree of unpredictability and makes it difficult to manage resources.

It is imperative to aim for a transversal regulation, capable of accompanying the growth of the human population and boosting the demand for fresh water for agricultural or industrial consumption and production.

Navigator pays special attention to these dynamics, complying with the regulations of the water resources management terms in detail. The forest area under its care is treated to privilege the health of the ecosystem.

The sustainable management of water resources is one of the major challenges of this century, both socially and from a perspective of collective well-being, economic and sustainable development.

Did you know that…

• The deadly impacts of extreme heat
  Increasingly intense heatwaves driven by climate change are causing massive mortality in several species. In Mexico, for example, spider monkeys fell from trees due to heat exhaustion, as temperatures exceeded 43°C. In Canada, a “heat dome” in 2021 killed an estimated 10 billion barnacles and 3 billion mussels.
• The first mammal wiped out by climate change
  The  Melomys rubicola rodent, endemic to the tiny island of Bramble Cay (Australia), was declared officially extinct in 2016. The most likely cause was the rising sea levels caused by climate change. This would have been the first mammal to go extinct as a direct result of human influence on the climate, according to a study published in the journal New Scientist.
• Half of the vertebrates have disappeared in less than half a century
  A conservation study indicates that the global population of vertebrates — including mammals, birds, reptiles, amphibians and fish — has fallen by about 52% over the past 45 years. An estimated 41% of amphibians and 26% of mammals are currently endangered.