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Greenhouses and the environment

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The use of greenhouses around the world has been growing dramatically.  A new satellite mapping exercise estimated the total land area covered with permanent greenhouses at 3.2 million acres, which is an area the size of Connecticut.  More than half of this is in China, where the growth of greenhouses has been driven by the rapid urbanization of the country and by a more prosperous population increasingly consuming produce like tomatoes, cucumbers, peppers, and eggplants.

The intensive agricultural methods employed within greenhouses can be harmful to local environments because of overtaxing water supplies and by polluting rivers and soils with nutrients, pesticides, and plastic waste.  But the effects of vast areas of plastic coverings on local temperatures can be even more dramatic, and often beneficial.

There are so many plastic and glass roofs in many areas that they are reflecting sufficient amounts of solar radiation to cool local temperatures.  Greenhouse roofs increase the albedo – the reflectivity – of the land surface typically by a tenth.

All these greenhouses are just the tip of the albedo iceberg.  Many farms now temporarily cover crops with reflective plastic sheets.  If these coverings are included in the satellite survey, the total reflective area would be about ten times greater – roughly the size of New York State.

A study in Almeria, on the Mediterranean coast of Spain, which grows about 3 million tons of fruit and vegetables annually, determined the cooling effects of greenhouses.  Weather stations amid the greenhouses showed an average cooling of 1.3 degrees Fahrenheit compared with the surrounding area.

Greenhouses are an accidental and benign form of climate engineering. The cooling provided by greenhouses is similar to the effect of white roofs in urban areas. 

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Could the Global Boom in Greenhouses Help Cool the Planet?

Photo, posted September 6, 2017, courtesy of Lance Cheung / USDA via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Moss And Carbon Storage | Earth Wise

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All plants, including algae and cyanobacteria, carry out photosynthesis. During the process of photosynthesis, plants remove carbon dioxide from the air and release oxygen to the air.  As a result, plants play a crucial role in the fight against climate change. 

According to a new study recently published in the journal Nature Geoscience, mosses – those tiny plants often found on the ground or rocks – might be important antidotes to climate change.  The study, which was led by scientists from the University of New South Wales in Australia and the Institute of Natural Resources and Agrobiology in Spain, uncovered evidence that mosses have the potential to store a massive amount of carbon in the soil beneath them.

The researchers found that mosses sequester around seven billion tons more carbon in the soil than is stored in the bare patches of soil typically found near them.  To put that figure in perspective, that is six times the annual global carbon emissions caused by global land use change, which includes things like deforestation, urbanization, and mining.  The researchers also found that moss-covered soil possessed heightened levels of vital nutrients and fewer instances of soil-borne plant pathogens on average compared to moss-less soil.

Mosses cover an area of more than 3.6 million square miles, which is similar in size to Canada, and can thrive in challenging environments.  The widespread presence and hardiness of mosses is why they can have such a significant impact on soil biodiversity and carbon sequestration. 

The research team hopes future work will focus on understanding the role of all types of vegetation, not just mosses and trees, in capturing carbon.

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Study: Modest moss supports billions of tons of carbon storage

Photo, posted August 23, 2017, courtesy of Peter Handke via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

City Greenery And Carbon Emissions | Earth Wise

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According to the United Nations, more than half of the world’s population currently lives in cities.  Projections show that the combination of urbanization and global population growth could add another 2.5 billion people to cities by 2050. 

Unsurprisingly, cities are a major contributor to climate change.  According to U.N. estimates, cities are responsible for 75% of global carbon dioxide emissions, with transportation and buildings being among the largest contributors. 

According to a new study of vegetation across New York City and some adjoining urban areas, photosynthesis by trees and grasses on many summer days absorbs all the carbon emissions produced by cars, trucks and buses, and then some.  In fact, on many summer days, the total carbon uptake in the region equaled up to 40% of a summer afternoon’s total emissions from all sources in the City. The results, which were recently published in the journal Environmental Research Letters, further highlights the critical importance of urban greenery.

Most previous studies have analyzed the carbon uptake of vegetation by looking at the contiguous tracts of green spaces, but this only comprises about 10% of metro areas.  Using detailed aerial radar imagery of New York City that mapped vegetation in unprecedented 6-inch grids, the researchers were able to include the other 90% of the metro area typically left out in most models. 

Since carbon uptake by vegetation only occurs during the growing season, green spaces in cities situated in warmer climates likely play a larger role in carbon uptake. 

As city populations swell around the world, every bit of urban greenery is critical in the fight against climate change. 

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New York City’s greenery absorbs a surprising amount of its carbon emissions

68% of the world population projected to live in urban areas by 2050, says UN

Photo, posted October 5, 2009, courtesy of David Orban via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Declining Flying Insects | Earth Wise

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In recent years, there has been increasing awareness of the global decline in insect abundance.  A recently published survey of the abundance of flying insects in the UK has revealed very troubling results.

The Kent Wildlife Trust and Buglife – two UK-based conservation groups – compared the number of dead insects on vehicles in 2004 and 2021.  In this Bugs Matter Citizen Science Survey, the data was collected by roughly 20,000 ordinary citizens using a smartphone app.

The results were that the number of flying insects in Britain dropped nearly 60% over that time period.  The insects declined most in England and Wales, with drops of 65% and 55%, respectively. 

It is possible that 2004 was a particularly good year for British insects and 2021 an especially bad one, but the findings of this study are consistent with other research around the world showing an alarming decline in insects.  A series of studies in 2019 found that the global mass of insects is shrinking by 2.5% a year and that insects are going extinct eight times faster than reptiles, birds, or mammals.

Insects face multiple overlapping threats including the destruction of wild habitats for farming, urbanization, pesticides, and light pollution.  On top of these things is climate change which is disrupting ecosystems in multiple ways.

Insects play a vital role in pollinating crops, consuming organic waste, killing pests, and as essential parts of multiple ecosystems.  Severe insect declines can potentially have dire global ecological and economic consequences.

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Flying Insects Have Declined by 60 Percent in the U.K., Survey Finds

Insect decline in the Anthropocene: Death by a thousand cuts

Photo, posted May 6, 2007, courtesy of Richard Giddins via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Strategies To Cool Off Cities | Earth Wise

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Heatwaves in cities are becoming increasingly common and increasingly intense.  The warming climate is a big factor, but it is the nature of our cities that really drives up temperatures.  Solar radiation stored throughout the day on asphalt and buildings is released slowly during the night, which generates significant heat stress.

A study carried out by a major Barcelona university and published in the journal Urban Climate looked at the effectiveness of various ways to mitigate the heating effects in cities.  In particular, the study examined the effects of the use of white roofs on buildings and the expansion of urban green areas with daily irrigation in the Barcelona metropolitan area.  It simulated various scenarios incorporating combinations of these two mitigation strategies.

The strategy with the greatest impact was a combination of the use of both white roofs and the addition of six urban parks, which is a target set by the Barcelona Urban Master Plan.  This scenario resulted in an average temperature reduction of 2.25 degrees Fahrenheit.  The maximum reduction occurs during the mid-afternoon with a reduction of 7 degrees and the combination still provides more than 3 degrees of reduction at 9 pm.  Reducing temperatures this way also results in a reduction in energy consumption, with 26% less spending on air conditioning.

The 2-pronged strategy combines the benefits of reducing the temperature at night due to more urban green areas with the reduction of daytime heat due to both the increased reflectivity of white roofs as well as the irrigation of the green areas.

The study demonstrates how modeling efforts can help urban planners to counteract the impacts of heatwaves, which are likely to increase with climate change and intensification of urbanization.

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White roofs and more green areas would mitigate the effects of heat waves in cities

Photo, posted January 16, 2011, courtesy of Sean MacEntee via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

A Better Solar Evaporator | Earth Wise

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Water security is a serious global problem.  Nearly 1.5 billion people – including almost half a billion children – live in areas of high or extremely high water vulnerability.  Less than 3% of the world’s water is fresh and demand for it is rising with increasing population growth, urbanization, and growing water needs from a range of sectors.

Researchers at the University of South Australia have developed a promising new technique that could help reduce or eliminate water stress for millions of people.  The technique uses highly efficient solar evaporation to obtain fresh water from seawater, brackish water, or even contaminated water.   According to the researchers, their technique can deliver enough daily fresh drinking water for a family of four from just one square meter of source water.

Solar evaporation has been the focus of a great deal of effort in recent years, but it has generally been found to be too inefficient to be practically useful.  The new technique overcomes those inefficiencies and can deliver fresh water at a fraction of the cost of existing technologies like reverse osmosis.

The system utilizes a highly efficient photothermal structure that sits on the surface of a water source and converts sunlight to heat, focusing energy precisely on the surface to rapidly evaporate the uppermost portion of the liquid.  The technique prevents any loss of solar energy and even draws additional energy from the bulk water and surrounding environment.

The system is built entirely from simple, everyday materials that are low cost, sustainable, and easily obtainable.

The technology has the potential to provide a long-term clean water solution to people who can’t afford other systems, and these are the places where such solutions are most needed.

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Sunlight to solve the world’s clean water crisis

Photo, posted November 13, 2016, courtesy of Steve Austin via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Shifting Ecosystems

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The Great Plains ecosystem has been shifting northward over the past fifty years, driven by climate change, wildfire suppression, energy development, land use changes, and urbanization.  The ecosystem is an area historically rich with grasslands and shrub steppe and is prime habitat for grassland birds.

According to a recent study published in the journal Nature Climate Change, the northernmost ecosystem boundary of the Great Plains has moved more than 365 miles north since 1970, amounting to about 8 miles a year.  The region’s southernmost ecosystem boundary has shifted 160 miles north, or about 4 miles a year.

The study used bird distribution data as an indicator of shifting ecosystem boundaries.  The researchers analyzed 46 years of data for 400 bird species across a 250-mile-wide strip stretching from Texas to North Dakota.  They tracked how the birds’ distributions changed as a measure of how these ecosystems were shifting.

While climate change has been a major driver of these ecosystem shifts since the 1970s, several other factors such as wildfire trends, land use changes, and invasion of tree species into grassland habitat have also played a role.  Like most things in ecological systems, the changes are likely to have multiple causes.  One cannot really separate causes like tree invasions, warming climate, and wildfires, as they are all interrelated.

Using bird distribution patterns for tracking ecosystem shifts could be a useful tool for scientists and land managers in the coming decades to give them an early warning of how habitats are changing in response to rising global temperatures and therefore allow them to take action to protect vulnerable species.

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Great Plains’ Ecosystems Have Shifted 365 Miles Northward Since 1970

Photo, posted March 24, 2017, courtesy of Rick Bohn / USFWS via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Declining Insect Populations

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There has been lots of discussion about the decline in bee populations and its dire consequences for agriculture.  We have also talked about the efforts to save the monarch butterfly, whose numbers have been dropping dramatically over the years.  But the rest of the insect world does not get much attention.  For the most part, we think of insects as a nuisance or as potential pests.

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