They are investigating in Alicante with pawlonias, in Pontevedra with Betula pendula and in Las Palmas de Gran Canaria with Laurus Nobilis. These are just a few of the studies carried out in different parts of the region to measure the carbon absorption capacity of certain plant species. Because not all of them have the same capacity to stabilize emissions, and moreover, some should be avoided in urban areas. Although most trees reduce air pollution, some species contribute to bad ozone formation in a deadly combination of isoprene released by organic compounds and polluting gases from traffic and solar radiation. Therefore, ideal in the context of global warming would be to program in detail what you want to plant in city gardens for environmental improvement while reducing fossil fuels or opting for much more sustainable mobility.
Biologist Vicent Calatayud Lorente from the Mediterranean Center for Environmental Studies (CEAM) has been collecting data for months to prepare a roadmap for tackling climate change. The trees most recommended for areas of high environmental pollution include jacaranda (Mimosifolia), linden (Tila platyphyllos) or mulberry (Morus alba). In contrast, false acacia (Robinia pseudoacacia), which is abundant in most Spanish parks, is one of the most isoprene emitters.
Date better than canary
The canary palm tree (Phoenix canariensis) is abundant on all islands as it tolerates the proximity of the sea and sandy soils, being one of the least suitable in residential areas with high motor traffic. If you have a choice, Calatayud recommends the date palm (Phoenix dactylifera) because Washingtonia is not one of the most recommended, like the poplar (Populus), which is found in large areas in many Chinese gardens. Eucalyptus (Eucalyptus globulus), which causes many problems in Galician forests, should be avoided due to its emissions. Its effects have disastrous consequences, as the composition of its leaves makes the soil poisonous, waterproof, dry and compact. In Asturias, new plantations are not permitted on lands not already occupied by this aggressive exotic invader native to Australia and New Guinea, given the consequences for biodiversity.
It will also prevent the formation of pollutants such as elm trees, ornamental plums, pears and apple trees. Other conifers, such as pines and cypresses, have intermediate emissions, but they have the advantage of removing pollutants in the winter, as they have leaves all year.
Meanwhile, the University of Alicante is among their latest projects to analyze the level of CO2 that a Pawlonias plantation located next to the Cemex cement company can sequester. It is a species that can hold ten times more carbon. The plot now covers eight hectares and has a total of 3,200 specimens. Its large leaves can capture 21.7 kilos of carbon dioxide a day and convert it to six kilos of oxygen. However, it is considered an exotic invader today, as it originally came from China.
The University of Oviedo has also developed mathematical models to determine how much carbon dioxide the most common species in the forests of Asturias and Galicia can absorb. The study compiles formulas for the ten most common species in the northwest of the peninsula, including chestnut (Castanea sativa), Celtiberian birch (Betula pubescens), beech and three oak species.
volatile compounds
The device, which Calatayud uses in various parts of the city of Valencia but can be exported to any point, then captures the leaves’ volatile organic compounds in a small tube and then measures their reaction, which is already in the laboratory. polluting gases of transport. The investigation was slowed by the restrictions of the pandemic as specimens had to be collected in city gardens, but new momentum is now expected.
In addition to cleaning the air, trees provide valuable environmental services by regulating temperature. That’s why the European Union’s new Forest Strategy envisions planting 3,000 million trees by 2030. Of course, taking into account the conditions of each region, betting on local varieties, more resistant and prepared for scenarios of water stress or environmental conditions. more extreme. Urban and urban areas are a priority due to greater environmental pollution. If the plan is successful, within ten years 10 percent of Europe’s surface should be firmly protected against 3 percent.
“Brussels wants to make cities greener, but it needs to be well planned”
The biologist looks for trees in cities that contribute the least to bad ozone formation.
The Mediterranean Center for Environmental Studies has spent twenty-five years researching extreme weather events such as heat waves and heavy rains, as well as climate change mitigation and adaptation. But also about air pollution and its effects in urban, rural and industrial settings. Biologist Vicent Calatayud is now studying the interaction between polluting gases from traffic and isoprene emitted by the flora.
“Europe suggests it in its climate change adaptation strategy to make cities greener, but we should also look at trees that emit less,” he says. “Obviously I wouldn’t take any of the existing ones away because trees are useful, but I would plan well for the future and take this new knowledge into account,” he says.
“The services they provide to us are indisputable, because they regulate the temperature and can reduce the temperature by one to three degrees compared to other residential areas in big cities,” Calatayud recalls. Despite this, he has repeatedly stressed that not everything should be relied upon in the role of carbon capturers, “but that gaseous emissions from vehicles should be reduced”.
“Plants and trees in a mountain region are not a problem in themselves, this problem only arises when you have a combination of volatile organic compounds with high levels of nitrogen oxides, that is, when tropospheric ozone is formed,” this expert explains.
The researcher recalls that plants emit a wide variety of Volatile Organic Compounds (VOCs). “Some of these protect the photosynthesis of leaves against heat. Others are emitted by flowers to attract pollinators, and also by fruits, whose fragrance will help animals distinguish ripe from immature. In addition, they represent a defense mechanism against insect pests: Plants stressed by attacks by certain insects increase the emission of certain VOCs to attract other insects that will attack that pest,” he notes.
Rafael Calatayud likewise explains that we must continue to bet on this type of work that will “allow progress in building more sustainable cities.” For example, shade sycamore trees (Platanus hispanica) are major emitters.