by Heather Rumble
Soil: Most of us rarely think about it and are likely unaware that the global degradation of soils is one of the biggest threats we face as a species (Gupta, 2019). Healthy soils provide the food we eat, filter the water we drink, protect us from natural disasters and pollution and form the basis of our habitat. Almost all soils on the planet have been altered and degraded by humans in some way; Even our last bastions of “natural” soil, in our virgin rainforests and at the poles, are under threat from commercial and illegal forestry, oil exploration and climate change.
A healthy soil is a living layer that changes everything that touches it. A teaspoon of soil from your back garden contains thousands of individuals comprising hundreds of species, all busy making soils work. But as fast as we’re discovering what lives in the soil, we are losing species. Nowhere is this fact more acute than on islands: Tropical islands punch well above their weight in terms of hosting biodiversity but suffer from the pressures of urbanisation, tourism and extreme weather events, with less scope to recover because of their isolation from the mainland.
A drive to understand more about soils, alongside the vulnerability of islands, is why I was in the British Virgin Islands this summer, working on a Defra Darwin Initiative project. The aim of the project was to undertake a basic survey of soil types across some of the 50 islands of the British Virgin Islands but also, crucially, to enable professionals in the British Virgin Islands to add to this map over time. To do this we set up a soil analysis laboratory within the Lavity Stoutt Community College, the first point of call for many islanders embarking on voyages of educational discovery in the BVI. My role was to set up a soil biodiversity lab, to train members of the civil service and college in basic soil ecology and to work with the National Parks Trust to understand how soil biodiversity monitoring could help them answer key conservation questions across the islands.
Gaffer gaiters a must!
While in the BVI, I had the opportunity to speak to islanders about the biggest challenges facing people and wildlife there: Intensive cattle grazing in the past has likely damaged the soils, not helped by the hordes of feral goats still roaming. Water availability is a key issue, with climate change noticeably reducing the availability of fresh water. One person told me that one of the ways they connect with nature is by growing things in their garden, but that this was getting more and more difficult with less rain and the slightly salty water provided by the desalinisation plant. Others waxed lyrical about the ways home composting was helping them tackle nutrient and water deficiencies in their gardens.
The National Parks team helped me take soil samples from three sites in the BVI: A desert island, dominated by cacti; A tropical forest a stones throw from the main town; and the Botanic Gardens, where the flora of the islands is well represented. It takes five days to process these in the lab and many more days to examine the catch!
Soils consist of many, many different kinds of organism including bacteria, protists, fungi, nematodes and microscopic insect-like creatures called microarthropods. It is the latter, or soil beasties as I like to call them, that I was focussing on in the BVI. They can be processed with basic kit and analysed with less taxonomic knowledge than some of the other soil groups. This makes them ideal as a monitoring tool for the community in the BVI.
The Tullgren funnels set up in the lab; This is the kit that extracts soil beasties from the soil.
With help from the participants in the training workshop we held at the end of the course, we recorded 17 different groups of organisms from across the three sites, likely encompassing over a hundred species. Even the desert sites supported soil biodiversity, albeit mostly hardy armoured mites of the kind that I also frequently find in cities. This illustrates how resilient this community of organisms is and the potential for recovery bound up in the soil; A little less compaction, a little less pressure from grazing on plants and the plants and soil will aid in each other’s recovery even in this harsh place.
Left image: A collection of soil beasties (mite top left; ant left and beetle right). Right image: Another mite, this one capable of tucking its legs under its shell. All at magnification. Images by Nandi Christopher and Joe Wells.
As well as the usual array of amazingly different coloured mites with whacky body shapes and the charismatic springtails (tiny relatives of crustaceans that can catapult themselves into the air), we also found pseudoscorpions, tiny relatives of scorpions with no stinger but perfectly formed little claws; and bristly millipedes, miniscule soil millipedes with, as the name suggests, tufty hairs in various exciting shapes. Both of these were a first for me as I usually work in harsh, low diversity environments (cities!).
One of the many pseudoscorpions encountered, shown actual size (left image) and under magnification (central image). Right image is a bristly millipede, Polixenida, under magnification.
But the biggest privilege of this trip was introducing others to the crazy world of life beneath our feet and working with such an engaged community of learners. Participants posed interesting questions, hypothesised about how this information could be applied and taught me new ways to photograph what I see under the microscope.
The trip is over but the lab and the knowledge of how to use it lives on in the BVI and forms part of their new soil analysis capability. I’m really glad to have been able to share our subterranean world with others and to have passed on some of the skills we need to employ to protect it. If some of the participants at the workshop, and perhaps those reading, look at the soil in their backyard a little differently from now on I will be a happy ecologist!
Many thanks to Richard Teeuw (PI, University of Portsmouth) and Melanie Daway (Dept. for Disaster Management, BVI) for organising the trip and making sure everything ran smoothly; Susan Zaluski (H. Lavity Stoutt Community College) for providing space, equipment and knowledge in relation to the lab; Nancy Pascoe (National Parks Trust) and the rest of the National Parks Team for organising site visits; Tom Heller and Sara Barrios (Kew Gardens) for the gaffer tape and plant knowledge and Nandi Christopher and Joe Wells (H Lavity Stoutt community College) for taking some amazing photographs. And, of course, to all the workshop participants for your enthusiasm and dedication! The project was funded by the DEFRA Darwin Biodiversity fund (DPLUS-160: BVI Multi-Purpose Soil Survey: informing environmental management and climate change mitigation).
References: Gupta, S. G., (2019) Land Degradation and Challenges of Food Security. Review of European Studies, 11(1), 63.