LAND
From the moment that the first plants started to colonise the rocky land, our blue planet started to turn green.
The new arrivals began to break down rock to create soil: a new material that would come to support vast ecosystems with millions of species.
Plants and soil together unlock energy and nutrients from the sun and land that, together with climate, give the different land surfaces on Earth their unique flavour.
Tropical rainforests, like the Amazon, are home to around half of all animal and plant species. Plentiful sun and rainfall supercharges plant growth, which in turn provides energy for the whole food web, powering ecosystems.
The frozen deserts of the Arctic hold one third of Earth's stored carbon.
Land is not merely soil, it is a fountain of energy flowing through a circuit of soil, plants, and animals.
Earth can be divided into eight major biomes: environments that have distinctive plants, soil, and animals.
The type of life that can exist in each biome depends heavily on the climate in that geographical region.
FROM TINY ACORNS
We live in a plant-dominated world.
Since conquering the land, plants have created soils and fossil fuels. They have changed the shapes of rivers and the way they deposit sediment, along with the composition of the atmosphere. Their activity has guided animal evolution since they too stepped out of the water looking for food.
It took the evolution of land plants – marked in the fossil record by the spores, seeds, and larger fossils left behind – to create stable ecosystems that existed entirely on land. It was a small step that changed global ecosystems forever.
The first plants had it tough, the ground they landed on would have been rocky and hard. Over time, the first plants created soil, and the first soils created new environments for plants, microorganisms and animals to exploit.
Fossils of early land plants
Grasslands now cover over 40% of the land on Earth and are present in almost every terrestrial ecosystem.
Trampled, grazed, cut and burned: grasses are some of the toughest plants on Earth.
The secret to grasses' success lies in the way they grow: quickly from the base rather than from the tips like most other plants.
They have spread to cover up to 40% of the land on Earth and are present in almost every terrestrial ecosystem. Around 66 million years ago, grassland habitats became common. Evolution responded, favouring animals with tough teeth, long legs, and acute peripheral vision.
Re-growth of grazed grass.
Grass doesn't just grow fast, it grows tough.
Phytoliths are shards of silica embedded in the tissues of the plant that are sharp enough to cut human skin and quickly wear down tooth enamel. Each mouthful of grass also comes with a sprinkling of soil. To withstand this constant attrition, grazing mammals have evolved wide, ridged teeth to cope with this gritty meal.
Away from close vegetation, tall prey animals on grasslands can see, smell and hear potential predators approaching. Large eyes on the sides of their heads give them almost 360 degree vision.
A microscope image of phytoliths in elephant grass. [Credit: Benjamin Gadet]
A microscope image of phytoliths in elephant grass. [Credit: Benjamin Gadet]
The Ugandan Kob (Kobus kob thomasi) is just one example of a grazing mammal.
Explore the interactive 3D model below to learn about the adaptations of its skull...
UNDERNEATH OUR FEET
Soil is one of the most important but overlooked foundations of life.
Every portion is unique. Soil across the globe contains different mixes of organic waste, minerals, gases, nutrients, and living organisms.
Soils are complex ecosystems in their own right.
They teem with microorganisms, fungi, plant roots, and small invertebrate animals like earthworms and dung beetles. Providing nutrients, carbon, and water, soils form the basis of all life on land.
Soil is made by living organisms
Plants and fungi live hand-in-hand
The composition of soil changes depending on what rock lies beneath it, the organisms that live on top and within it, and the climate it is exposed to.
Generations of plants live, die and rot down to form the rich organic constituent of the soil, called humus. Roots push into cracks and break rocks, and organic acids dissolve the rock beneath to create mineral particles in the soil. Animals introduce air as they burrow through soil. Water creeps down through soil from rainfall and is sucked up from rocky reservoirs below.
The composition of soil changes depending on what rock lies beneath it, the organisms that live on top and within it, and the climate it is exposed to.
Generations of plants live, die and rot down to form the rich organic constituent of the soil, called humus. Roots push into cracks and break rocks, and organic acids dissolve the rock beneath to create mineral particles in the soil. Animals introduce air as they burrow through soil. Water creeps down through soil from rainfall and is sucked up from rocky reservoirs below.
Earthworms are not native to all soils.
Their ecosystem engineering may be producing surprising effects in environments to which they have been introduced. Sugar Maples are a commercial crop, planted for their wood and sap, and artificially dominate some North American forests. Earthworms introduced accidentally in plants imported from Europe may be linked to a recent dieback in Sugar Maple growth. The worms clear the forest floors of leaves and leave shallow Sugar Maple root systems vulnerable to drying out. The loss of Sugar Maples would have serious effects on the Sugar Maple food web, reducing food and shelter for some species. But the effect on the wider forest food web may be positive as Sugar Maples are replaced over time with a mix of native woodland trees better for long-term forest resilience.
CHANGING ECOSYSTEMS
Where land is created by Earth processes, new opportunities for life are revealed.
Around 4.5 million years ago, a new bridge of land was formed between North and South America. These two continents had previously existed independently, separated by a deep mass of water and each had its own unique fauna and flora. The new land set in motion a north-south exchange of species on a massive scale driving new evolutionary changes, as well as extinctions.
But the effect of the sliver of new land reached beyond the Americas: the new causeway also separated the Pacific and Atlantic oceans, shutting down movement of ocean life as well as the warm currents that had previously flowed from the Pacific into the Atlantic. This resulted in the formation of the Gulf Stream that now warms the Atlantic coasts of America and Europe.
Even after cataclysmic geological events, life finds a way to rebuild.
A rare opportunity to study this in real-time came after the 1980 eruption of Mount St Helens in the northwestern United States.
Mount St Helens has been one of the most active volcanoes in North America in recent centuries, with at least twenty eruptions in the last 4000 years. The 1980 eruption devastated the surrounding landscape, allowing researchers to study short- and long-term ecological responses, and track the recovery of damaged ecosystems. Now, nearly 40% of the world's published research on plant and animal responses to volcanic eruptions is based on data from Mount St Helens.
The recovery of life around Mount St Helens started almost immediately, but the response was varied and dependent on prior conditions. Those organisms that survived the initial blast had a strong and lasting legacy on the ecosystem communities that subsequently developed. Terrestrial ecosystems around the volcano became impoverished due to the loss of vegetation and burial of soil by ash. However, the high concentrations of nutrients that washed into aquatic ecosystems made them more productive than before.
Survival, and the ability to recover, depended on distance from the blast site, the condition of the ecosystem at the time of the blast, where animals resided, or whether plants could regenerate from roots that had not been destroyed. The patchwork of conditions created a rich diversity of responses and ecosystems.
In the Spring of 1980, Mt St Helens experienced an earthquake that triggered a pyroclastic flow, a debris avalanche, volcanic mud flows, and an ash plume.
In the Spring of 1980, Mt St Helens experienced an earthquake that triggered a pyroclastic flow, a debris avalanche, volcanic mud flows, and an ash plume.
The eruption below the top and side off the previously symmetrical volcano: Mt St Helens is now 400m shorter and missing its north face.
The eruption below the top and side off the previously symmetrical volcano: Mt St Helens is now 400m shorter and missing its north face.
Explore the interactive below to learn about how different species recovered after the blast:
Ecosystem recovery was left to chance. The establishment of certain plant species and fungal networks determined the nutrient status of water and soils, which dictated which plant life could develop and, in turn, which animal communities could survive. Life persisted in the face of difficult challenges; recreating stable conditions, or establishing new ones.
Built with Shorthand
