Investment in trees yields pretty good returns

According to the estimates of the World Health Organization (WHO), 9 out of 10 people around the world breathe polluted air. City dwellers started suing the authorities for the lack of effective policies to tackle smog.

Soot, dust and other dirt particles are affecting our health slowly but surely — WHO claims that impure air is responsible for seven million premature deaths each year. Considering that about 60 million people die every year (57 million people in 2015), air pollution is the cause of about 12 per cent of all deaths. That’s a lot. These factors very rarely kill us directly — they usually impact us in the form of lung cancer, strokes, heart attacks, chronic respiratory diseases.

However, the popular belief that pollution, which is harmful to people, primarily comes from factory smokestacks and exhaust pipes is not true. If we were to believe the findings of Professor Richard E. Peltier from the University of Massachusetts, in the United States the greatest source of the PM 2.5 fine particulate matter, which is very harmful to people (these are so-called suspended particles or atmospheric aerosols with a diameter of up to 2.5 micrometers), are fires, and in particular forest fires (1.7 million tons per year). Other sources of particulate matter include agriculture (the processes of ploughing and harvesting), which produces 988,000 tons, as well as dust, which is the source of 964,000 tons. The processes of combustion related to energy production are only the fourth most important source responsible for 726,000 tons, while transport is the fifth source in America, responsible for 339,000 tons. Various smaller sources are responsible for 335,000 tons overall, while industrial processes produce 285,000 tons of particulate matter.

In light of the very rapid demographic growth, the ever-growing overall and per capita energy needs, and the absolute dominance of traditional energy sources based on the combustion of carbon compounds, there is no instant or single-factor remedy for this problem. Instead of basing our hopes on the promise of miraculous technologies, and instead of focusing our attention and resources almost exclusively on renewable energy sources, it would be more effective to adopt a more comprehensive, holistic approach, allowing us to see both the different causes and the different solutions to the problem. They may be less spectacular or more demanding at times, but they are effective.

Planting trees really pays off

It is a fact that is commonly known, to the point of being obvious: trees filter the air, converting deadly carbon dioxide into oxygen. An American team of scientists therefore decided to measure the impact of tree stands on human well-being. For this purpose they used IT tools known as “i-Tree Tools” which analyze, among other things, aerial photos. The software allows us to count trees, measure their height, crown sizes, and the area covered with leaves/tree canopy. On that basis, it provides data that is used to evaluate the impact of tree stands on air purification, water absorption, optimization of the energy needs of buildings, noise suppression, pollination of plants, fulfilment of recreational needs, etc.

Based on research which covered 35 out of 45 so-called megacities, each with a population of over 10 million people, Dawid Nowak, PhD, from the USDA Forest Service, Professor Theodore Endreny, from the State University of New York, and Scott Maco, from the Davey Institute, estimated that each USD1 spent on planting trees in metropolises provides an annual return on investment of USD2.25. In other words, if you spend the USD1m on trees, in each subsequent year you can expect various, though sometimes difficult to capture, long-term benefits amounting to over twice as much as what you invested.

A particularly careful analysis was conducted on 10 megacities on five continents. This allowed the scientists to assess that 1 square kilometer (sq. km) of urban tree cover brought savings of USD83 to the average citizen (the amount is expressed in USD according to Purchasing Power Parity, taking into account the differences in the purchasing power of an Egyptian from Cairo and, on the opposite end of the spectrum, a Californian from Los Angeles). Calculated per 1 sq. km, the absolute savings on the costs of treatment from diseases caused by pollution would amount to USD930,000, the savings on the storage of excess water would reach USD20,000, and the savings on the energy used for heating and cooling would amount to USD478,000. However, the greatest benefits stem from a phenomenon which, as we’ve already established, seems pretty obvious — the fact that trees capture carbon dioxide. The median savings for megacities amounted to USD7.9m annually.

The data presented above do not have to be taken literally. The main value of the study is determining the order of magnitude of the benefits obtained from urban tree stands, in accordance with the principle — often detrimental to economics — that we don’t appreciate what we can’t measure.

There can never be too many trees, although some would also negate that. One of such deniers is the new member of the United States Environmental Protection Agency (EPA), Professor Robert Phalen, from the University of California in Irvine, who said that “modern air is a little too clean for optimum health”. He certainly exposed his ignorance, but his attitude was not the most radical example to date. In 1981, during an official address, President Ronald Reagan stated that “trees cause more pollution than automobiles do”.

Even the phenomenon that occurs in the Great Smoky Mountains (along the Tennessee and North Carolina state lines) does not justify the spreading of “bad news”. That mountain range owes its name to the fog that frequently hangs over the terrain. It is generated due to the abundance of optically active chemical compounds (i.e. ones that undergo rapid oxidation in the presence of light) such as terpenes and isoprenes, which are released from the multitude of resinous trees growing in these mountains. During heat waves that frequently occur there, these processes accelerate, and the isoprenes become a catalyst for the rapid conversion of nitrogen oxides into ozone. The latter protects the earth from ultraviolet radiation when concentrated high in the stratosphere, but when it builds up at lower altitudes, it takes the poisonous form of the so-called photochemical smog.

Does this mean that Ronald Reagan was onto something after all? Ozone is formed at temperatures above 25°C from the decomposition of nitrogen compounds, which, in the current conditions, are primarily derived from automotive exhaust fumes and from agricultural activity. This means that trees do have their minimal contribution to the formation of ozone, but to blame them for the deterioration of the environment is preposterous.

In Poland, trees and forests are treated with a great esteem. However, this is mostly an impression rather than certainty. No detailed studies have ever been conducted in the country, as a result of which only rudimentary data concerning urban tree stands are available. For example, the Greenery Board of the Capital City of Warsaw knows that the entirety of municipal greenery covers approx. 40 per cent of the capital’s surface area, while the parks situated within the city limits have a total area of about 800 hectares. The city has introduced the “Green Streets” program, which provides for the planting of 18 thousand new trees along the city’s major streets. Meanwhile, the municipal authorities are increasingly frequently planting more mature trees that are 6 to 10 years old and have a circumference of 16 to 18 cm and a height sometimes reaching seven meters. Thanks to the “One Million Trees” application, the city invites the residents to suggest the possible locations of new plantings. In this field things are getting better rather than worse.

Burning wood

However, we are still cutting trees faster than planting new ones. It takes years to “produce” a forest or a park, while it only takes one heating season to burn it. The International Energy Agency (IEA) estimated that in 2016 “traditional solid biomass”, i.e. wood, straw, but also cow dung, fulfilled about 5 per cent of the global demand for so-called primary energy. The share of biomass appears to be low, but it should be noted that it is still two times higher than the share of so-called renewable energy sources. About 2.5 billion people, or one-third of the global population, are permanently dependent on dirty (as they emit soot and other harmful compounds) “kitchen household fuels” derived from the collection of brushwood or tree felling. Would it be possible to replace — within a reasonable time — the bonfires and hearths with portable induction cookers powered by, for example, solar energy? This would also entail huge costs, for example, associated with the construction of the infrastructure.

According to the Poland’s Institute for Structural Research, as many as 12 per cent of the population in Poland faces problems with heating their houses, and with access to hot water or electricity. This is usually associated with the lack of funds (so-called energy poverty) and is one of the reasons behind phenomena such as the unwillingness of Polish households to get rid of the home furnaces commonly known as “smokers” or “stinkers”, the burning of junk fuels, and the winter smog in hundreds of Polish cities.

What is interesting, however, is that air pollution resulting from household combustion affects both poor and wealthy areas. The adviser to the Danish Ecological Council, Kaare Press-Kristensen, presented data according to which in the years 2000-2015 domestic wood burning increased two and a half times in that country. This is probably also due to the fact that in Denmark taxes are high or very high, while the tax rate on wood is zero. Although wood burning only meets 3 per cent of the primary energy consumption in Denmark, it contributes to two-thirds of the contamination with fine particulate matter.

So, maybe the answer is in biofuels? Several decades ago the developed world carelessly took this path, following Brazil’s example, and started the large scale implementation of so-called biofuels in the form of ethanol and esters added to petrol and diesel oil for the alleged purpose of improving the condition of the environment. Biofuels were supposed to reduce the relative consumption of conventional fuels, but they are simultaneously causing great harm in other areas. They are produced from cereals, rapeseed oil and palm oil. Approximately 38 per cent of American corn harvests are processed into ethanol.

The cultivation of that crop requires huge amounts of fertilizers produced from natural gas. Moreover, crop monocultures decrease soil fertility. In other regions, tropical forests are being destroyed to make room for palm plantations. The sale of fuels with a 15 per cent admixture of ethanol is banned in the Unites States in the summer, because of the fear that it contributes to the smog. In the context of biofuels, which are also persistently implemented in the EU and in Poland, it’s worth calling for a comprehensive analysis of the benefits versus negative effects.

Some want heat, while others want cold

There is one more argument for avoiding stereotypes, generalizations and so-called only correct solutions, which over time turn out not to be as great as they seemed. If the world continues its march forward, one particularly dangerous development from the environmental perspective could be the increasingly quick reduction of energy poverty in the undeveloped regions of the world, inhabited by the majority of the global population. It just so happens that these are also the warmest parts of our planet.

The IEA estimated in this context that approximately 1.6 billion air-conditioning units installed around the world, along with fans, consume about one-fifth of all the energy used in all buildings. To put it differently, air conditioning accounts for one-tenth of humanity’s total energy consumption. In two decades the consumption of electricity for the purpose of cooling the air is projected to be three times higher. If there is no significant — or truly revolutionary — breakthrough in the area of renewable energy sources, which are still in their infancy, the energy emancipation of Africa, Asia and South America will require higher and/or more efficient use of conventional fuels.

Contrary to the dominant view — and disregarding for a moment the entirely separate issue of the profitability of maintaining and developing coal mining in Poland — it should be emphasized that Poland’s production of electricity in large hydrocarbon-burning power plants will, for a long time, be easier, cheaper and more efficient than relying on renewable energy sources, which are still very expensive in general, and in their initial stages of development.

This does not mean, however, that we shouldn’t try to enforce the modernization of household combustion which is responsible for the smog. The Poland’s Prime Minister’s Plenipotentiary for the “Clean Air” program, announced that a law concerning quality standards for solid fuel boilers would be passed by the end of the year. After that, it will be necessary to enforce the new regulations, which could be cumbersome, not very successful, and expensive.

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