Forests that serve the climate

Adding climate, water and syntropy to re-forestation and greening

An exciting new opportunity is opening up on the horizon of tree-planting and ecological restoration in general. The powerful effects that vegetation has on water and energy cycles, and therefore on climate itself, can form a synergy with greening, re-forestation and the functional restoration of biodiversity, ultimately leading to the reestablishment of a friendly, bountiful environment. We list here a few crucial biogeophysical benefits to the climate of restoring native vegetation.

1 Carbon wet-sinking

Reforestation and greening efforts tend to revolve around the carbon paradigm as if sucking up carbon from the atmosphere alone could repair or fix climate disorder. Plants are certainly important in removing CO2 from the air since they store it in biomass. However, plants as living organisms depend umbilically on other environmental factors to survive and thrive. Chief among these factors, water availability affects the efficiency of the carbon sink and is also instrumental in determining how long carbon is retained in biomass. Thus, the progression and longevity of carbon sequestration in reforestation projects cannot be properly assessed without also framing the hydrological conditions and climatic environments of each location. Therefore, vegetation that promotes and sustains a humid climate can also capture and maintain more carbon in its biomass.

2 Water sponge

Compacted soils absorb little or no rainwater. Episodic or seasonal rains that fall on impermeable soil are thus lost to runoff, generating floods and draining uselessly into the oceans. The vegetation in general, especially the trees, are excellent infiltration promoters. Being able to pierce through compacted soil deeply with their roots, trees also create a layer of organic debris, forming a root-mat that attracts and maintains a wide variety of burrowing insects and an immense population of decomposing organisms, which transform the hardened soil into moisture welcoming soft earth. In addition to a series of hydrological benefits, the water retained in the landscape promotes plant productivity for a prolonged period and, therefore, participates in the plants' ability to condition and favor the climate.

3 Air Cooling

The trees pump water from the soil and emit water vapor through the canopy, increasing the humidity of the air. Such an effect, strange as it may seem, cools the surface. A calorie is a measure of the thermal energy needed to raise the temperature of 1 gram of liquid water by 1 degree Celsius. Only 100 calories are absorbed to raise a gram of water from freezing zero to boiling 100 degrees Celsius, while five times as much energy is required to convert that gram of liquid into a gas (vapor). Thus, evaporation absorbs the thermal energy from its surrounding environment, decreasing the local temperature. Plants transpire in large quantities during the day, a figure reaching up to 1000 liters per day for a large mature tree in a tropical forest. Such reverse air-irrigation of sorts can have the same cooling effect as three 36,000 BTU/hour air conditioning units blasting at full capacity. In other words, a single tree can continuously cool about three two-story houses in a hot climate. The 400 billion trees in the Amazon could cool all the buildings on the planet many times over.

4 Heat Hauling

Unlike a typical air-conditioning unit - which absorbs indoor heat and dissipates it in nearby outdoor air - plant transpiration captures the surrounding heat, packing it in vaporous water. Like a bee laden with pollen after visiting a flower, the water vapor upwelling from a transpiring forest is charged with latent heat absorbed from the surface. And also like the bee that flies for kilometers to its hive, the water vapor laden with energy is carried to higher altitudes in the atmosphere and to far away latitudes. Heat transport is an extraordinarily important and necessary part of the cooling effect promoted by forests.

5 Warming into cooling

CO2 gas in the atmosphere traps about 20% of the planet’s outgoing heat. Water vapor can trap up to 80% of the outgoing heat, varying a lot in space and time. At face value, more water vapor in the air should not be good, as it aggravates global warming. But only if the water vapor stays stagnantly dissolved in the air. However, unlike CO2, vapor in the atmosphere condensates and releases latent energy. This release of energy sets winds in motion and emits radiant heat.

6 Radiative shooting

Radiant heat released during condensation of water vapor high up in the atmosphere escapes more easily into space than heat emitted from the surface. This happens because there are fewer heat trapping gases above a certain altitude, if compared to their concentrations in the lower atmosphere. Water vapor functions like an elevator, picking heat up from the surface and dissipating it at higher levels, thereby cooling the planet.

7 Rain maker

Condensing water vapor forms clouds that eventually precipitate as rain. However, for dissolved water vapor to start condensing, certain critical conditions must be met, such as a low enough temperature and the presence of airborne particulate matter that functions as condensation seeds, initiating the agglutination of gaseous water molecules into liquid droplets. Trees release organic gases - the volatile smells - which become very important sources of condensation seeds. In this way, trees supply all the raw ingredients that make up rainfall.

8 Biotic Pump

Condensation of water vapor releases part of its latent energy as a lowering of pressure. That mechanical effect forms and propels low level air currents that function as large conveyors moving matter and energy around the globe. Such movements are especially important in transporting moisture from the oceans inland, as well as in transporting heat from tropical latitudes towards the planetary radiators located on both poles.

9 Storm tamer

A rough, uneven forest canopy forms a very efficient windbreak, offering a means for the winds to dissipate their kinetic energy, thus preventing the occurrence of energetic circulations like tornados and other similarly destructive events.

10 Friendly and safe Climate

Joining all the above-mentioned effects together, plus many other ecologically mediated services provided by vegetation in general, and especially by forests, will result in a more hospitable climate.

Author: Antonio Donato Nobre.