Science Matters by David Suzuki

Exploring the world under our feet

Aug 23, 2000

One of the hallmarks of the human species is our intense curiosity. It has driven us to explore the far reaches of the globe, the depths of the oceans and even pushed us into space. It has also rewarded us with tremendous insights into the workings of our own bodies, the structure of matter and the birth of the universe.

Yet in spite of our impressive capacity to learn and explore, we still know very little about many of the basic underpinnings of life on Earth. In fact, some of the most poorly understood habitats on the planet are right under our feet – the top metre of soil in our forests, fields and gardens – and just over our heads in the forest canopy.

The composition of our soils is actually crucial to how the ecosystems above ground function. In fact, some of the most important interactions between plants occur underground. Similarly, interactions between organisms in the forest canopy are also crucial because this is where photosynthesis takes place – where sunlight is captured and converted into chemical energy – one of the greatest energy pumps on the planet.

As human populations expand, resources become more scarce and the climate changes, it becomes more and more important for us to understand how organisms interact in these crucial areas. Then we may better learn to work within the boundaries of natural systems without degrading them.

Researchers have recognized this need. Last week, the president of the Ecological Society of America called for a major expansion in soil ecology research. That’s an important step, because we have a long way to go before we understand the intricate relationships between soil organisms, plants, animals and the atmosphere.

For example, scientists are only now beginning to uncover the dynamics of mycorrhizal fungal communities. These amazing organisms intertwine themselves with the fine roots of trees, forming a symbiotic (mutually beneficial) relationship. The fungi feed off of sugars (which are produced in the tree canopy through photosynthesis) from the tree roots, while extracting vital nutrients like phosphorous from the soil and making them available to the tree in a usable form.

The fungi are also believed to protect the trees from pathogens, increase water absorption and release a protein that helps stabilize soil. Over time, the fungi can expand into a great filigree-like web that covers a huge area of soil. In fact, researchers believe that mycorrhizal fungi effectively connect trees with up to 1,000 times more soil than just the roots themselves!

Mycorrhizae are also a key component in the transfer of carbon from plants into soil. This is an important factor to consider because, as we increase the concentration of carbon dioxide in our atmosphere from burning fossil fuels, more carbon will be taken up by plants and find its way into the soil.

But how will this increase in carbon affect soils? That’s a difficult question, according to a recent article in the journal Nature. At this time, soils are an important reservoir for carbon, but if that changes due to an increased rate of carbon cycling, soils could become less effective at storing carbon, causing more carbon dioxide to be released, which could speed up global warming.

Another important question is how that extra carbon could affect soil biodiversity. Just one square metre of soil can contain thousands of species of bacteria and other microorganisms. Soil is alive – a complex community of organisms. Researchers are just now starting to figure out where organisms go and what they do. It’s a difficult process – as one researcher points out, you can’t put a radio tracking collar on a bacterium.

But then, scientific discovery is rarely easy. On the surface, soil may seem like a mundane research topic, but there are literally thousands of discoveries waiting to be made underground.

Perhaps it’s time we turned our curious eyes downwards.