Biodiversity is contributing in achieving food security and improved nutrition?
While I think this is obvious, from many years working with small-scale farmers in SE Asia on "rice-based farming systems" helping them convert to "organic" (agroecological) methods which support ecological health and abstain from chemical use. It is clear this shift brings a quick and impressive return of the diverse flora and fauna that live in healthy rice ecosystems. Fish are usually the most valued resource that returns, but also shrimp, crabs, good tasting snails and diverse wild vegetables (edible weeds). All of this is natural biodiversity that is oppressed in a chemical intensive system but which returns with agroecological management and provides valued secondary - highly nutritional yields. Beyond this these farming systems promote increased integration, (and thus increased agricultural biodiversity). Bunds are not sprayed with herbicide but often widened and used to plant small fruit trees, herbs, and vegetables- providing additional healthy food. While perhaps not a key point here, our project also identified many factors from these more diversified ecological "Rice-based Farming Systems" promoting increase resilience - specifically climate change resilence. Diversity of yields is one of these factors.
In terms of Mainstreaming Biodiversity in Agriculture (and more)
As part of a collaborative effort of the Agricultural Biodiversity Community with Ileia / Farming Matters magazine we develop the March 2014 issue "Cultivating Diversity" I think all of this issue (attached below) is relevant to your topic.
The article I submitted on pages 24-25, looks at what has been limiting the expansion of biodiversity-friendly agricultural practices.
Now 4 years later, while I still feel what I have written is valid, I see much more of a deteriorization of the (traditional) knowledge on how to use the diverse resources in diverse agroecological / forest garden systems. (Such as bamboo varieties for building, for cooking with, for weaving, for making ties, for eating, etc) or the many dye plants, many traditional herbs, many wild/ perennial vegetables. This links strongly with aging farmers whose children and grandchildren are not involved in farming. And then with how biodiverse farming can provide a good livelihood for capable young people.
While we have many good examples that are working well, I am aware of some limitations and needs. Such as a greater availability of small-scale appropriate technology / machinery for working in biodiverse farming systems such as forest gardens that could help with increase labor constraints everywhere.
Where a (sustainable) production system played a key role for the conservation of the biodiversity surrounding it?
From my experience what is known as "Forest Gardening" or "Organic Agroforestry" has perhaps the most impressive role in conservation of biodiversity for land-based systems. In our network it is normal to have more than 100 intentionally grown "crops" in these systems. However for scaling up (and which is the case with our gardens and most in our network) one or more "key economic crops" is within the forest system (along with a high diversity of food crops, herbs, spices, hardwood trees, etc.)
Well-documented are the Forest Gardens of Sri Lanka. In terms of watershed/ forest restoration on a larger scale, the success of the Organic Forest Coffee Project initiated by Earth Net Foundation in Chiang Rai province, led to the signing of an MOU with Khuechae National Park and Lam Nam Kok National Park in 2016 to revitalize and restore the degraded forest of the National Park- an area of 3,200 hectares over 10 years together (2016- 2025) through the practice of Organic Agroforestry. Coffee is the key (understory) economic crop.
An article I wrote (link below) describes the forest gardening system of farmer colleague Ms. Kanya Duchita in Chantaburi with key economic crops of Para rubber and tropcial fruits (Durian +) that co-exist with wild elephants (and many other wildlife).
http://regenerationinternational.org/2018/01/15/forest-gardening-space-place-wild-elephants
Mr. Michael Commons