How Many Trees Do We Actually Need On Earth?

We seem to hear about deforestation rates frequently, and the impact they can have.

But, how many people stop to consider how many trees we actually need on Earth in order to sustainably support humans, animals and the environment?

Some people might say as many as possible, but that answer is too simplistic, and misses the other very important and specific points that need to be considered.

In this guide, we discuss how many trees we might need on Earth, and attempt to put some numbers and reason behind potential answers.

 

Summary – How Many Trees Do We Actually Need On Earth?

There’s various ways we can measure the amount of trees on Earth:

Total number of individual trees

The total area of land with tree or forest cover on it

Tree density (number of trees per square area of land)

+ other measurements

 

Earlier estimates of total trees on Earth (in about 2005) put the total number of trees on Earth at about 400 million trees.

Some of the latest estimates as of around 2015 suggest there are 3.04 trillion trees on Earth

The Arctic has the densest tree cover on Earth, but the tropics and subtropics (warmer climates) support 43% of all trees on Earth

It is estimated about 15 billion trees are being cut down or lost every year

It is estimated only about 5 billion new trees are being replanted every year

The net loss of total trees is about 10 billion trees a year

Tree cover, and tree loss or replacement rates can differ from region to region around the world

 

Some points about how many trees we might need on Earth going forward into the future might include:

– We might want to plant at least 10 billion more trees a year than we are now so we are running at a net neutral for annual tree numbers, and not a loss.

This number likely needs to be higher as more developed countries progress economically (and need more resources), and world population numbers increase.

[So, there’s got to be consideration about net annual tree numbers, population growth, consumption rate, and so on]

 

– The type of trees we are talking about definitely matter when considering tree numbers.

Man made forests can easily be re-planted and are less valuable.

However, primary tropical forests and savannas are almost impossible to replace (or take a very long time to replenish and restore), and are incredibly valuable for the biodiversity they have.

We might want to protect these types of forests and trees as a first priority.

Also, the tree species, tree qualities, tree size, the types of trees a local area can support, and other characteristics of the tree may matter

 

Trees provide many benefits that solve different problems

Just as one example, along with soil and the ocean, trees and the world’s vegetation are responsible for being major carbon sinks.

Trees also produce oxygen, help with water and air quality, and help with nutrient cycling and soil health.

We may want to identify the problems that are most important to solve, and manage tree numbers based on solving these specific problems.

With this approach, the number of trees and the amount of tree cover we may need in different regions on Earth may vary.

 

Some of these specific problems that trees help solve, and how many more trees we might need to address the problems might include:

 

Trees & Climate Change – Absorbing Carbon From The Atmosphere

Some studies estimate 1.2 trillion more trees on Earth would absorb enough carbon dioxide to remove the last 10 years worth of human carbon dioxide emissions

 

Trees & Cycling Nutrients, & Soil Health

Dependent on local conditions – different soils are degraded to different extents, so soils which are most unhealthy or most degraded may need more trees

 

Trees & Water Quality

Dependent on local conditions – water sources in different areas are of different qualities, so water which has the most severe quality problems may benefit from more trees

 

Trees & Oxygen Production

Every year, we might need one tree on Earth to provide enough oxygen for 10 people.

The actual number of trees might be less when you consider that plankton and land based vegetation also provide oxygen to breathe

There’s currently almost 8 billion people on Earth, and that number could be up to 10 to 13 billion by the year 2100.

 

Trees & Air Quality and Air Pollution (Absorbing Air Contaminants)

Different cities and countries in the world have different levels of air pollution and air quality.

Those with the poorest air pollution and air quality might consider planting more trees and vegetation to absorb some of these air contaminants

Some cities have already added vegetation to do this.

 

Trees For Human Products & Services

Trees are used all over the world for different products and services.

Big cities and small rural and local communities/population rely on trees for not only good and services, but their livelihood.

Obviously, trees need to be replenished at a rate that allows humans to sustainably consume and use the products and services we need to live, or to actually live in their local area

 

Tress & Biodiversity, Wildlife & Ecosystems

Primary forests, tropical forests and savannas have heavy concentrations of biodiversity.

We should protect them as a priority over man made tree cover.

It’s sometimes impossible to replace or restore natural forests and natural tree cover.

Whereas, with human made tree cover, these tree areas can be replenished (but trees still take time and resources to grow, and we lose the benefits that trees provide once they are cut down and take their time to grow).

 

Other notes about trees are:

– Plankton, and on-land vegetation like seaweed, trees and land based plant life produce all of the world’s oxygen

– Trees might not be the only option to address some problems.

– Other plants like bamboo provide some of the same benefits of trees (like carbon sequestration), but grow much quicker.

So, it may be worth us planting more bamboo in some areas compared to trees if it helps us achieve objectives quicker and easier than trees would.

– The theoretical number of trees we need on Earth could decrease in some instances if we are able to address a problem at it’s root cause e.g. stopping air pollution in the first place, reducing emissions in the first place, recycling more paper and wood based products so we need less trees etc.

– The number of trees needed in a particular geographic region, such as a State or province within a country, may differ from place to place.

So, each local area should be assessed individually

The mass planting of trees is not without it’s challenges – we’ve mentioned some of those challenges in this guide on deforestation.

 

How Many Trees Are Currently On Earth?

One global estimate in 2015 was:

[As of 2015 there were previous estimates of 400 billion total trees on Earth, but that estimate increased with a new study to 3.04 trillion trees on Earth, or around 422 for each person on the planet]

However, stats can differ country by country (as opposed to a global level):

[there were] three billion trees in the UK, or around 47 for every Briton [in 2015]

– independent.co.uk

 

How Many Trees Are Cut Down/Lost Per Year? (Deforestation Rates)

Around 15 billion [trees] are lost every year due to deforestation, forest management and changes in land use

– independent.co.uk

 

How Many Trees Has Earth Lost Since The Beginning Of Human Civilisation?

… since the start of human civilisation, around 11,700 years ago, the total number of trees has fallen by around 46 per cent

– independent.co.uk

 

What About More Recently – Have We Gained Or Lost Tree Cover Over The Last Century?

Tree cover is area of trees, rather than total number of trees.

 

Recent estimates suggest Earth has more tree cover today than it did 35 years ago:

… research suggests an area covering 2.24 million square kilometers – roughly the combined land surface of Texas and Alaska, two sizeable US states – has been added to global tree cover since 1982.

This equates to 7% of the Earth’s surface covered by new trees.

– weforum.org, nature.com

 

Also note that the types of trees matter (there is a distinction between tree cover and forest cover.)

Forests are probably more valuable than man made trees.

And in the above numbers, man made trees are being planted to replace natural forest area. 

As noted by weforum.org:

[tree cover and forest cover] are not equal in biodiversity.

Primary tropical forests and savannas harbour a wealth of flora and fauna which is lost when these areas are cleared.

And man-made forests do not compensate for the damage and degradation done to ecosystems through land clearance.

The research attributes 60% of all land-use change throughout the study period directly to human activity, with the remaining 40% caused by indirect factors like climate change

 

So, when we look at deforestation and new trees being planted, we have to look at the types of trees being removed.

Tropical forest cover and savanna areas might be far more worrying to lose compared to man made and woodland tree cover (such as industrial timber plantations, mature oil palm estates and other specifically planted forests).

 

Also, note that there are different tree cover gain and loss rates in different regions of the world, such as Oceania, South America, North America, Europe, Asia and Africa.

Places like South America might experience large losses, while Asia might experience large gains.

 

Tree Density In Different Regions In The World

Tree density is the number of trees per square area of land …

The densest areas of tree coverage are the boreal forests of the Arctic, whereas deserts support the fewest trees per hectare.

Even so, cold places have just 24% of the trees, whereas the tropics and subtropics support almost 43%.

The rest are distributed throughout other places, including temperate zones.

– sciencemag.org

 

How Else Can We Measure Trees On Earth Other Than Number, Cover & Density?

Tree size, species identity, and tree qualities matter hugely in accounting for the importance of forests and trees outside of forests

… particularly the sizes of trees, because that determines how much biomass—and consequently carbon storage—in each one

– sciencemag.org

 

How Many Trees Are Replanted Or Re-Grown Per Year?

[it is thought] about 5 billion new trees are planted or sprout annually, yielding a net loss of 10 billion

– sciencemag.org

 

What Are The Benefits Of Trees & Forests For The Earth, Humans, Animals & The Environment?

We listed the benefits of trees and forests in the summary above and also in the sections below.

But, specifically, trees might offer some of the following:

 

store huge amounts of carbon

are essential for the cycling of nutrients

are essential for water and air quality

and are used for countless human services

– independent.co.uk

 

Trees provide food, energy and income to help communities achieve long-term economic and environmental sustainability.

Trees also filter the air and help reverse the impacts of climate change.

In just one year, a mature leafy tree produces as much oxygen as 10 people inhale

– earthday.org

 

Forests are important to humans, not just for their products, but also for their ability to foster biodiversity, store carbon, preserve water quality, and perform other ecosystem services.

Up to 45% of the carbon stored on land may be tied up in forests.

– sciencemag.org

 

Trees & Reversing Climate Change/Carbon Dioxide Absorption – How Much Carbon Do Trees Sequester & Store?

… humans emit 26 gigatonnes of CO2 per year while CO2 in the atmosphere is rising by only 15 gigatonnes per year

… much of human CO2 emissions are being absorbed by natural sinks [like the ocean and vegetation]

– skepticalscience.com

 

Since the industrial revolution, about 375 billion tonnes of carbon have been emitted by humans into the atmosphere as carbon dioxide (CO2)

– carbonbrief.org

 

A tree can absorb as much as 48 pounds of carbon dioxide per year and can sequester 1 ton of carbon dioxide by the time it reaches 40 years old

– projects.ncsu.edu

 

[A very rough estimate of how many additional trees we would need to combat climate change is] 1.2 trillion new trees

There’s 400 gigatons [of carbon] now, in the 3 trillion trees [on Earth], and if you were to scale that up by another trillion trees that’s in the order of hundreds of gigatons captured from the atmosphere – at least 10 years of anthropogenic emissions completely wiped out

– treehugger.com

 

Trees & Oxygen Production

One large tree can provide a day’s supply of oxygen for up to four people.

– projects.ncsu.edu

 

Trees, Cycling Nutrients & Soil Health

A nutrient cycle (or ecological recycling) is the movement and exchange of organic and inorganic matter back into the production of matter.

In forest environments, there is an exchange of nutrient elements such as hydrogen, nitrogen and oxygen among the soil, plants and animals living within the environment.

Trees and other plants take up mineral and non-mineral nutrients from the soil through their roots.

These nutrients are stored in the leaves, flowers and other parts of plants.

The nutrients are either transferred to animals when animals eat the plants or they are transferred back into the soil.

– mdocs.skidmore.edu

 

Trees & Air Quality and Air Pollution

[Trees absorb] Toxins such as nitrogen oxides, ammonia and sulphur dioxide through their leaves, bark and roots.

This improves the air quality in the microclimate around the trees and contributes to a healthier and cleaner environment overall.

– thepresenttree.com

 

Trees & Biodiversity, Wildlife & Ecosystems

The diversity of life that a tree can support is incredible.

A single tree in the tropical rainforest can house up to 2,000 different species of insects, birds, amphibians, reptiles, mammals, fungi, mosses and epiphytic plants!

– greenwave.cbd.int

 

Trees & Services/Products For Humans (& Supporting Human Livelihood) 

Hundreds of food products (fruit, coffee, nuts, etc.) and food additives (for ice cream, chewing gum, etc.) come from trees.

Each year, one person uses wood and paper products equivalent to a 100 foot tree 18 inches in diameter.

Over 5,000 products are made from trees.

– projects.ncsu.edu

 

Trees & Water Quality

Trees and vegetation can help reduce water quality problems in communities by decreasing stormwater runoff and soil erosion. 

Trees also absorb some of the nutrients in the soil that would otherwise be washed away

– articles.extension.org

 

Sources

1. https://www.independent.co.uk/environment/how-many-trees-are-there-on-earth-10483553.html

2. https://www.earthday.org/campaigns/reforestation/

3. https://www.weforum.org/agenda/2018/08/planet-earth-has-more-trees-than-it-did-35-years-ago/

4. https://www.nature.com/articles/s41586-018-0411-9

5. https://www.sciencemag.org/news/2015/09/earth-home-3-trillion-trees-half-many-when-human-civilization-arose

6. https://projects.ncsu.edu/project/treesofstrength/treefact.htm

7. https://skepticalscience.com/human-co2-smaller-than-natural-emissions-intermediate.htm

8. https://www.carbonbrief.org/doha-infographic-gets-the-numbers-wrong-underestimates-human-emissions

9. https://www.treehugger.com/climate-change/heres-how-many-trees-it-would-take-cancel-out-climate-change.html

10. https://articles.extension.org/pages/67763/urban-forests-improve-water-quality

11. http://mdocs.skidmore.edu/crandallparktrees/ecosystem/nutrient-cycling/

12.  https://thepresenttree.com/blogs/news/how-trees-reduce-air-pollution

13. http://greenwave.cbd.int/en/resources/tree-biodiversity

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