You might think that there is not much science in growing a tree, but there are many things to consider here.
A tree-planting or reforestation project should aim to achieve multiple goals: biodiversity improvement, benefit to soil, water and food production, empowerment of local communities. Failing to include them is one of the most common causes of an unsuccessful reforestation project. For that reason we only work with suppliers that engage them, or are indeed primarily led by the local communities.
The choice of tree species is also crucial. We avoid monoculture plantations, although we will consider them on a case by case basis (one of our projects includes monoculture plantations that we felt was balanced with a sustainable long-term income model for local population as well as protection and more natural restoration of riparian zones.) We consider criteria such as: are the tree species native? Are they resilient to climate change? In agroforestry context: do they bring ongoing benefits to the farmers such as nuts or leaf fall fertiliser, which increase the likelihood of the tree left standing outside of the contractual obligations?
One thing that is often forgotten in the climate offset world but we use as criteria is the albedo effect. Albedo is about how much sunlight is absorbed vs. reflected by the Earth’s surface. Relatively dark conifer trees absorb more sunlight compared to some alternative vegetation or bare grounds, especially during snow cover. Planting the wrong tree in the wrong place can lead to more warming than cooling because the albedo effect outweighs the cooling effect of the carbon removed and stored in the trees.
