Tree Nation, with a small dynamic team based in Barcelona, Spain, is building an online community dedicated to fighting climate change by simply... planting trees!

Partnering with UNEP (UN Environment Programme) and its Plant for the Planet campaign since 2006, Tree Nation's tree-investing community is growing rapidly with over 90,000 people and 120 European and international companies involved.

And as of today, 388,864 trees have been planted.

Tree Nation's model is a bit like Kiva's -- you choose the project you want to invest in and you can then follow the progress of your project.  You can invest as little as 5,5€ (or even participate for free).  But instead of investing in social entrepreneurs, you're investing in trees.  And instead of getting repaid in money, you get rewarded by knowing that you are contributing to combatting desertification, deforestation, and climate change.

Tree Nation has currently four major projects in Niger, Nicaragua, Colombia, and Madagascar.

Let's say you decide to invest in some trees.  You choose the Niger Heart project, Tree Nation's ambition project of planting 8 million trees in the shape of a giant heart by 2015 (currently, just over 300,000 trees have been planted for this project).

You decide to plant 2 Acacia senegal trees (7€ / tree).  The Acacia senegal has a long root system, which restores and enhances the fertility of the soil.  Moreover, it serves as food for livestock and produces resin and gum.  The Acacia senegal has a life expectancy of 30 years and absorbs 180 kg of CO2 over it's lifetime (15 kg/year for 12 years.  Trees absorb most CO2 during their growth period).

You can then follow the growth of your trees and the progress of the Niger Heart program.  Easy, right?

If you are specifically concerned about offsetting all your CO2 emissions, you can become a "serial planter", investing on a monthly basis.  To completely offset your footprint, Tree Nation estimates you will need to plant 24 trees / year which will cost 14€ / month.

Tree Nation bases its offset calculations on the the official European average for CO2 emissions: 9 tons of CO2 / person / year (source: eurostat).

9 tons of CO2 emitted is equivalent to 24 trees absorbing approximately 20 kgCO2 for a period of 20 years => 24*20*20.

Tree Nation has also engaged companies such as Google, The Economist, and Procter & Gamble to become tree planters through its corporate program.  The Economist for instance, plants one tree for every new susbcriber in Europe, Africa, and the Middle East.  New readers are then invited to follow the progress of their trees and get actively involved.

Overall, Tree Nation is a clever and innovative social network that allows individuals and companies to easily get involved in fighting climate change -- even while sitting on your couch at home.  And for those who are motivated, you can visit the tree sites during plantation period and get your "hands dirty".

Plant a tree in a couple clicks.  Let's do it!