Hello Bhs; Biodiversity of all taxa is declining in nearly all regions of the world. The degree of loss is related to desertification, land conversion, and human population growth. However, the degree of loss is not uniform across regions. You'll need to look at particular regions. I'd recommend reading in international journals like Nature or Science. They review aspects of the problem in nearly every issue. Best regards. Jim Des Lauriers

You count species and compare them over time :)

Thank you Professor

Decreasing and being permanently eliminated worldwide, wherever there are humans that are farming and wherever domesticated grazing animals exist and are making their impacts. Our activities have a massive impact on not only decreasing biodiversity, we are like a biological cyclone, remaking whole ecosystems in only a dozen human generations--like California 100% native cover in 1769, now 99.999% exotic cover in 2022. The same with most of the rest of North America. I did a three painting about this issue at https://www.ecoseeds.com/art4.html about the "Spatial Extinction" of biodiversity in Arabia, California and the Mojave desert, and that would also apply to the lands of North Africa.

The diversity of plants on the planet earth is an important resource for food, shelter, and agriculture. About thousands of plant crop species have been identified, developed, used and relied on for the purpose of food and agricultural production in human history. These plants include bushes, grasses, herbs, shrubs, trees, vines, ferns, and mosses. Through the process of photosynthesis, plants provide us with the oxygen which we breathe and the sugars that provide the primary fuel for life.

There is a great variation in the biodiversity, resulting from human and ecosystem interaction for certain food and development for the survival of the human population, regardless of the pests, climate fluctuations, diseases, droughts and other unexpected environmental events. Currently, there are only a few crop species which provide us with food and essential energy requirements for the total human population all around the world. These crops include rice, wheat, maize, cereals, pulses, etc. As per the requirement on this moderately small number of crops for global food security, it will be essential to maintain a continuity of these plants species along with the increasing environmental stress and to provide opportunities for the farmers to breed more amount of crops that can be cultivated under unfavourable conditions such as poor soil, salinity, drought, flooding, and extreme temperatures.

Biodiversity in Plants and Animals - Its Importance (byjus.com)

You need to know what an intact ecosystem is supposed to look like. Then do a survey and see what is left and what is missing. And this can be done on a large scale, like continent wide, like a Megatransect that I did in 1997 that you can see at https://www.ecoseeds.com/megatransect.html and found that in the Western States, the native grasses were mostly gone: (% gone)

California 99%, Idaho 94%, Nevada, Utah and Wyoming 60-68%, etc.

The other side of biodiversity, was due to animal grazing, the lack of undisturbed pristine examples of ecosystems, like less than 1% of the lands in California, Idaho, South Dakota and Wyoming. Only the Rocky Mountains in the alpine areas above 3,000 meters were left fairly intact.

You cannot judge the existence or absence of biodiversity, until the human impacts are removed for a few years, so you can see what is actually still there.

In particular for Morocco, get soil samples from a grid, like on 10 km. apart in each direction, and do a native grass phytolith study... to see what used to grow not that long ago in areas that look barren today. The grass phytoliths are silica fossils from the grass leaves that last a long time, so you can study what grew in an area decades to centuries ago. Picture from https://confluence.org/confluence.php?lat=33&lon=-2 and you can see from the remaining vegetation, that this areas was a solid native grassland not too long ago. Even though there does not seem to be much to graze in this picture, this area is probably still grazed at least part of the year, and by putting up a small 5 x 5 meter exclusion fence, you might see the dormant native seeds sprout up again, once they are protected from grazing.

I guess that use of common ecological indices and biomass are the best indicators.

I found this on this website https://royalsociety.org/topics-policy/projects/biodiversity/is-the-rate-of-biodiversity-loss-increasing-or-decreasing/

Currently, 37,400 animal and plant species are known to be threatened with extinction – roughly 28% of the 134,000 assessed by the International Union for Conservation of Nature (IUCN) Red List. The true figure is expected to be far higher when accounting for the total number of species on the planet.