Why plant a fruit tree rather than an ordinary tree?
Because a fruit tree does everything an ordinary tree does (shade, holding the soil, capturing carbon) and also produces something the other does not: food, and an income for the person who looks after it.
This difference completely changes the relationship between the tree and the people who live around it.
What both have in common
Any tree holds the soil, limits erosion, gives shade, plays a part in the water cycle and stores carbon. On these points, a mango tree and a forest tree are equal.
What only a fruit tree brings
A harvest is both food and something that can be sold. For a household, that can mean a direct food supply and a seasonal extra income.
It also gives a very concrete reason to look after the tree. Nobody waters a tree that earns them nothing; people water the one that feeds their family.
The real problem with tree planting
Many reforestation campaigns announce millions of trees planted, and many of those trees do not survive. The reason is almost always the same: nobody on the ground has an interest in keeping them alive.
The fruit tree solves this problem in a simple way: it makes looking after it rational. The survival of the tree and the interest of the family point in the same direction.
The link with Sadaqa Jariya
The idea of Sadaqa Jariya assumes something that keeps being useful over time. A tree that dies after one season serves nothing and no one, whatever the intention was.
Choosing a fruit species, and planting it where its harvest has real value, is therefore not an agronomic detail. It is what determines whether the gesture lasts.
The limit, honestly
A fruit tree needs more attention than a forest tree, especially in the first two years. It needs more water and is more sensitive.
That is the price of what it brings. It requires teams present on site, and it is also why a fruit plantation costs more than a tree simply put in the ground and forgotten.