Leaving fall leaves on the ground can be beneficial for pollinators, as they provide a valuable food source during a time when other resources may be scarce. Pollinators, such as bees, butterflies, and other insects, rely on the nectar and pollen from plants for sustenance, and many of these insects also use leaf litter as a place to overwinter and as a source of food. By leaving fall leaves on the ground, you can create a more diverse and resilient ecosystem that supports pollinators and other beneficial wildlife. Additionally, it can also be beneficial in terms of soil, plant health and reducing erosion. 

Leaving fall leaves on the ground can be beneficial for gardens in several ways:

1. Leaves can act as a natural mulch, helping to retain moisture in the soil and suppress weeds.
2. The leaves of some trees, such as oak and hickory, are slow to decompose and can be left on the ground to act as a natural mulch.
3. The leaves can provide important nutrients to the soil as they decompose, helping to improve soil health and fertility.
4. Leaves can also protect the soil from erosion and help to improve soil structure.
5. Leaves can be used in composting to make a rich soil amendment.
6. The fallen leaves will be a good habitat for beneficial insects and other wildlife that can help keep pests in check.
7. Leaves that are left on the ground can serve as a food source for earthworms which can help to improve soil structure and fertility.
8. Leaves can also help to reduce the need for other types of soil amendments, such as fertilizer, and can help to save you time and money in the long run.

It is also important to note that not all leaves are good for gardens. Leaves from certain trees, such as walnut and eucalyptus, can be toxic and should be avoided.