China – Gardening at Last

Continuing our soil theme from yesterday, today’s post focuses on pollutants in soil.

Map of the study area and watersheds near village Kibber in the high-altitude region of Spiti, Trans-Himalaya, northern India. The colored polygons represent eight watersheds spread over c. 40 km2. The native and livestock watersheds are demarcated by high ridges, escarpments and ravines, that establish replicates of two types of herbivore-assemblages (dominated by either livestock or by native herbivores). Credit: (2022). DOI: 10.1101/2022.02.07.479355

Antibiotic-laced dung ‘harming soil quality’

Antibiotics used on livestock can impact microbes in the soil and negatively affect soil carbon, reducing resilience to climate change, claims a study conducted in India’s trans-Himalayan region. Results of the study, published in Global Change Biology, found native herbivores such as yak, bharal (blue sheep), kiang (wild ass) and ibex in the Spiti valley, in India’s Himalayan state of Himachal Pradesh, to be healthier for soil carbon than livestock, which includes cattle, goat, sheep and horse. “Microbial carbon use efficiency was 19% lower in soils under livestock,” said Sumanta Bagchi, an author of the study and assistant professor at the Center for Ecological Sciences of the Indian Institute of Science in Bangalore.

Supporting evidence in the study pointed to a link between veterinary antibiotics and soil microbial decline. “Our study suggests that conserving native herbivores together with better management of livestock can go a long way towards improved soil carbon stewardship to achieve natural climate change solutions,” says Bagchi. “Our paper focused on climate impacts linked to the use of antibiotics for livestock rearing but there are other undesirable consequences such as the accelerated evolution of antibiotic resistance which is a global trend,” they added.

Home ‘compostable’ plastic doesn’t fully break down

Compostable plastic that has not fully disintegrated in compost bin. Credit: Citizen scientist image from bigcompostexperiment.org.uk.

In a UK-wide study, researchers have found that 60% of home-compostable plastics do not fully disintegrate in home compost bins, and inevitably end up in our soil. The study also found that citizens are confused about the labels of compostable and biodegradable plastics, leading to incorrect plastic waste disposal. These results highlight the need to revise and redesign this supposedly sustainable plastic waste management system.

A new OECD report shows that plastic consumption has quadrupled over the past 30 years. Globally, only 9% of plastic waste is recycled, while 50% ends up in landfills, 22% evades waste management systems, and 19% is incinerated. Compostable plastics are becoming more common as the demand for sustainable products grows. The main applications of compostable plastics include food packaging, bags; cups and plates, cutlery, and bio-waste bags. But there are some fundamental problems with these types of plastics. They are largely unregulated, and claims around their environmental benefits are often exaggerated.

In a study published in Frontiers in Sustainability, researchers at University College London have found that consumers are often confused about the meaning of the labels of compostable plastics, and that a large portion of compostable plastics do not fully disintegrate under home composting conditions.

Soil pollution in natural areas similar to urban green spaces

Microplastic debris. Credit: Roberto Ruiz (UA)

An international study, recently published in Nature Communications, shows that soil in urban green spaces and natural areas share similar levels of multiple contaminants such as metals, pesticides, microplastics and antibiotic resistance genes around the world. Soil contamination is one of the main threats to the health and sustainability of ecosystems. The work was carried out by more than 40 authors from research centers and universities in Spain, China, Switzerland, Australia, Germany, Chile, South Africa, Nigeria, France, Portugal, Slovenia, Mexico, the United States, Brazil, India and Israel. The team has collaborated with ecologist Carlos Sanz Lázaro and Nuria Casado Coy, researchers at the Ramón Margalef Multidisciplinary Institute for Environmental Studies (IMEM), and experts in the study of plastic and bioplastic pollution.

As the article reports, soil pollution is currently associated with vehicle emissions, industrial processes, pesticide treatment and plant diseases, as well as poor waste management. It is therefore to be expected that urban green spaces are more influenced by pollutants than natural ecosystems, which are geographically distant from human activities. However, the study has shown that hazardous pollutants (metals, pesticides, microplastics and antibiotic resistance genes) can be dispersed by air transport, uncontrolled waste disposal and even rainwater running off the surface of a piece of land and into natural ecosystems.

Microplastics, typical pollutants of anthropogenic (human) origin, are also ubiquitous in soils of urban green spaces and natural ecosystems around the world. Surprisingly, as reported by Sanz Lázaro, they have found similar proportions of the form and polymer type of microplastics in natural areas and urban green spaces, which further supports the idea of a spread of anthropogenic pollutants through ecosystems. These microplastics, often originating from cities, affect distant areas by atmospheric transport, with fibers being the main form of plastic particles suspended in the atmosphere in cities such as Paris, London and Dongguan (China). The fibers generally consist of polyester and polypropylene from synthetic fabrics, ropes, and nets.

Farming out: China’s overseas food security quest: Drought has plunged water levels in China to a once-in-decades low. Some Chinese cities, reliant on hydropower, are going without air conditioning as temperatures soar and residents walk on dry riverbeds. But the most catastrophic consequences could be in store for the country’s food supply.

On Aug. 23, four government departments warned that the autumn harvest, which supplies 75% of China’s grain, is under “severe threat” due to the drought. “The rapid development of drought superimposed with high temperatures and heat damage has caused a severe threat to autumn crop production,” they said in a statement.

The anticipated poor harvest is the latest in a series of food supply shocks that have buffeted global markets this year, following the war in Ukraine that caused global shortages of everything from sugar to cooking oil.