One answer, is that it is all based on three things, 1.) Domesticated grazing animal impacts, 2.) Removal of the local Pseudomonas host plants that create the local rainfall, 3.) Dryland-farming conducted in marginal arid areas. These three items have created what we call "deserts" that previously were arid grasslands and savannah, north of the Equator.

The first concept is-- All of the "deserts" north of the Equator are man-made, with those three items--the grazing of domesticated animals, cutting down the Pseudomonas host plants and drylands farming--Are the three "dials" that dial up or dial down the "native-greenness" where the local native biodivsersity can flourish, or must struggle to survive.

The change from thriving grassland and savannah can occur rapidly over large areas of the planet, in less than four human generations, like the SW of the USA or the 150,000 square miles of the State of California, that went from arid grasslands and savannah to barren desert scrublands and woodlands where the native understory became spatially extinct, that you can see at http://www.ecoseeds.com/desertgrass.html

They're all different , each with their own unique biodiversity

Thanks Craig Carlton Dremann for your valuable and informative answer.

In particular where you are located, the Indus Valley Civilization made the mistake of cutting down the Pseudomonas host trees to bake the bricks for their 1,000 cities and 5 million people.

Then, that made the rain stop, and all of those cities and their people had to abandon their homes. See the Discover magazine article https://www.discovermagazine.com/planet-earth/does-rain-come-from-life-in-the-clouds and the attached image from my flier at http://www.ecoseeds.com/8-ending-civilization.pdf -

Plus, you can see the difference in "green" --when you conserve the Pseudomonas host plants, in the mountains above Salalah, Oman with rivers and lakes--and then nearby Oman where you do not, and produce a moon-scape at http://www.ecoseeds.com/cool.html

As a rule, deserts are divided into 3 groups – extraarid, arid and semiarid. Accordingly, semiarid deserts (or semi-deserts) will be the greenest and most productive.

Thanks Craig Carlton for providing useful information

The question is WHY are deserts in the northern hemisphere extra arid, arid and semiarid, when all summer long from the Thar desert of India and across Pakistan, and across Afghanistan, Iran and Iraq, and through the sands of Arabia, and all across the Sahara from Egypt to Morocco--monsoonal moisture from India is flying westward across those lands every week, but not producing any rainfall?

Three major reasons: 1.) Lack of Pseudomonas host plant vegetation to produce the rain clouds, and barren soil. The barren soil contributes two important factors--bare soil absorbs the sun's heat, then heats up the air, whereas if the soil had only a few cm. of native plant cover, that would insulate the soil and cool the soil surface by as much as 40 deg. F. (from 54 deg C to 32 deg C.), thereby cooling the air temp. 2.) The raised air temp. changes the dew point, and in order to have rain clouds form, the dew point must match the dry air temp. This is one of the main reasons for the creation of "deserts" from western India to Morocco.

3.) Barren soil and winds get atmospheric dust airborne, and atmospheric dust kills rain clouds, and can even stop Category-5 cyclones from making landfall. See the interaction between atmospheric dust and the Cyclone GONU at http://www.ecoseeds.com/newGONU.html when the Pakistan-Arabia Dust Cloud trapped the cyclone in the Straits of Hormuz?

Thanks Craig Carlton Dremann

for providing worthwhile information about deserts.

Here is today's image of the "Pakistan-Arabia Dust Cloud" from https://www.nrlmry.navy.mil/shared-bin/display_image.cgi?URL=/aerosol_web/globaer/ops_01/india/current.gif

Between China and Morocco, there are about 6-8 permanent dust clouds keeping the rain cloud from forming over what is currently "desert" areas, and we need to give each one names, so we can talk about them.

The Sahara dust clouds are at https://www.nrlmry.navy.mil/shared-bin/display_image.cgi?URL=/aerosol_web/globaer/ops_01/sahara/current.gif and the Gobi desert clouds are at https://www.nrlmry.navy.mil/shared-bin/display_image.cgi?URL=/aerosol_web/globaer/ops_01/mongolia/current.gif

These dust clouds are the most powerful weather modifying agency on the planet, about to create deserts wherever they are allowed to exist, and they are all man-made, by allowing our domesticated grazing animals eat every native plant down to the dust, that then gets airborne?

Interesting phenomenon Craig! Restoring the original massive forests again - but WITHOUT Pseudomonas bacteria, would you think would NOT have an impact on the meso- or macroclimatic conditions of those areas?

We are gradually getting aware of the massive deforestation due to baking of bricks, building ships, having goats and sheep eat all tiny green etc. that has taken place since the year 5000 BC, which easily can explain desertifications and formation of deserts due to massive reduction in evaporation, shade, loss of hydrological connectivity, increase in wind speed etc... Does Pseudomonas help in formation of rain drops? THX L

Deserts are barren, unproductive vast mass of land. Nowadays some countries of the world are trying to utilize desert lands for natural production by planting trees. Some examples of such are: (1) Successful planting being tried in Dubai deserts, (2) Green revolution of deserts in Israel, (3) Reforestation to anti desertification in California, (4) China is finding ways to turn deserts into forests. The Idaho desert is green and productive by virtue of solar energy.

Biological productivity is the total amount of biomass produced by a population or community per unit of time per unit of area. At the same time, there is a distinction between primary – the biomass produced by autotrophs (green plants) during photosynthesis; and secondary – the biomass obtained by heterotrophs per unit of time per unit of area. Primary production is divided into gross (equal to the total number of photosynthesis products for a certain period of time) and net (equal to the difference between the gross and the part of it that was used for plant respiration). In herbaceous plants, 40-50% is used for respiration, and in trees – 70-80% of the gross primary production. The primary production of terrestrial ecosystems is usually estimated by the annual growth of plant biomass (net production). Each ecosystem, taking into account natural factors, is characterized by certain values of primary biological productivity. Minimum values of biological productivity fall on arid areas (deserts, semi-deserts).

The productivity of herbage in salt marshes varies widely. Saline vegetation is characterized by a high ash content, reaching 40-55% in the fleshy salt flats of the desert zone. The ash content of semi-dry salt pans is 20-30 %, and that of xerophytic sagebrush is 10-20 %, while in plant communities of unsalted soils (cereals and legumes) it usually does not exceed 10 %.

Desert soils often show a fairly high content of certain nutrients. The biomass of plants varies from as high as in grasslands, in some thickets of semi-desert semi-shrubs and shrubs to very low. Since the desert is dominated by shrubs, the proportion of nutrients contained in the biomass that enters the fall annually is less than in grasslands, but higher than in the forest. There are relatively many nutrients in the biomass and dead residues: the amount of ash elements is from 4 to 7% with a high content of sodium and chlorine in some plant species. The content of the most important nutrients (phosphorus, nitrogen, potassium) in the tissues is usually the same as in deciduous forest trees. Deserts are low-productivity ecosystems with biomass containing a superabundance of certain nutrients. Only a small portion of the nutrients that are abundant are circulating, and they can even accumulate in the tissues, while the circulation of other nutrients, especially nitrogen, looks relatively compressed.

Pasture productivity is maintained due to the presence of such meadow grasses in the herbage, which are able to grow quickly after grazing and give a steady output of green mass during the entire pasture period. When using a corral grazing system, the energy of tillering of grasses, especially grassroots, increases. Grazing in the semi-desert and desert plays a great positive role in the seed renewal of plants, contributing to the shedding of Mature seeds and simultaneously embedding them in the soil.

In the deserts of Central Asia, under the protection of black saxaul forest belts, the productivity of ephemeral-sagebrush herbage increases by 4 times. Sprigs of black saxaul are eaten by sheep and camels in winter. This type is being introduced in the Astrakhan region and Kalmykia. Saxaul form a good enough shelter for the animals in adverse weather.

The productivity of the soil is also influenced by grazing. Excessive grazing changes the structure of the pasture ecosystem (some valuable plant species disappear, the number of rodents and locusts increases, etc.), leads to the destruction of sod and soil destruction. As a result, erosion increases and anthropogenic deserts are formed, which are "aggressive" and very difficult to agricultural development.

Loss of productive land to desertification throughout the world now make up 50-70 thousand square miles per year, and the total area of "artificial desert" arising from human activity — more than 8 million square km. Deserts are advancing on the steppe, the steppe, in turn, on savannas, savanna — tropical forest. Scientists have estimated that during the period of active human activity, irreversible losses of land resources reached 20 million square kilometers, which is almost one and a half times the current arable area of the planet.

Agriculture in the deserts is impossible without irrigation. With irrigation, the desert, with its abundance of sunlight, can become very productive. The size of the desert phytomass is diverse.

The floodplain soils of the desert zone have not been studied enough. Significant areas of floodplains of large rivers in the desert zone are occupied by salt marshes and meadow-saline soils. The vegetation of tugai (floodplain forests) is highly productive. The biomass of tugai communities is very significant — up to 1000 C / ha or more. The fall is more than half of the biomass, so there are formed soils with a high content of humus.

In the conditions of desert irrigation, when water ceases to be a limiting factor, the type of soil becomes of paramount importance. Where the soil structure and nutrient content are favorable, the desert can be extremely productive due to the large amount of sunlight. However, due to the high cost of building and operating irrigation systems, the unit cost of grown products may be high. Very large volumes of water must flow through such an ecosystem, otherwise salt accumulation in the soil may begin (as a result of high evaporation rates). As the watered ecosystem "ages", the increased demand for water causes a "spiral of inflation"; there is a need to build new water pipelines, which increases the cost of production and leads to more intensive exploitation of underground or mountain water sources. In the deserts of the Old World, it is easy to find the ruins of ancient irrigation systems everywhere. In many cases, no one knows why they have fallen into disrepair and why the "garden of Eden" has become a desert again. These ruins remind us that a watered desert cannot flourish forever.

Tree planting in a desert is a mistake--you need to work backwards up the ecological ladder first--and always use local genetic material. First colonizing annual forbs and annual native grasses, then perennial native grasses and perennial forbs, then shrubs, then as frosting in the cake--the local native trees.

Meanwhile, you need to keep the grazing animals away.

And in California where I live, no replanting of our deserts yet, and the Idaho deserts, which were originally perennial grasslands, are being destroyed by wildfires caused by introduced weed grasses from Europe, which have moved in where grazing has caused the native grasses to become extinct, and only leave the shrubs with barren spaces between them.

And in order to make this whole project work, you must add the native Pseudomonas host plants, that create the rainfall for your planting to thrive--see https://www.discovermagazine.com/planet-earth/does-rain-come-from-life-in-the-clouds

Plus, if you are working within one of the atmospheric Dust Cloud areas, like western India or Pakistan, or Arabia or North Africa, you also need to replant enough native ground cover to stop the Dust Cloud from forming, otherwise that dust will cancel out your rainfall--see http://www.ecoseeds.com/cool.html

Thanks Munira Nasiruddin for your informative answer about the green deserts of the world.

I did a study on Cultural Ecosystem Services in the Negev Desert in Israel.

Article The 'desert experience': Evaluating the cultural ecosystem s...

Apparently, this is one of the only deserts that is undergoing a de-desertification (or reverse desertification process) in the world, pushing the aridity line backward. As far as I understand, it is because of the farming and forestation efforts in the area but it is a good idea to look further into it.

Thanks Yael Teff Seker for sharing your worthwhile views regarding the question under investigation.

Lorenz Hübner - Huge difference between forests replanted without the Pseudomonas host plants, and one that is. See https://www.discovermagazine.com/planet-earth/does-rain-come-from-life-in-the-clouds

WITH pseudomonas host plants...you can see the effects in the relatively tiny strip of relict forest 5 x 25 miles in the mountains above Salalah, Oman, in my study at https://www.ecoseeds.com/cool.html -- When monsoonal moisture from India goes over, it rains--outside of that forest the most barren deserts on the planet, including the infamous "Empty Quarter?

Which by the way, before the domesticated animals ate the host plants away about 2,500-5,500 years ago, had one of the largest lakes in the world 300 feet deep, and was the site of Ptolemy's map's famous lake located in Yemen.

For every arid area on the planet...we MUST discover what the host plants are ASAP, and start replanting them right now, so we do not become as barren and lifeless as Mars in places? Also see https://www.ecoseeds.com/salalah.html

Thanks Craig Carlton Dremann

for your valuable and informative response.