How better understand and model the multiple and interlinked roles of soils in our planet life, to make the best use of them?

A good way to assess the societal impact of soils on all these aspects is to estimate it in cost/benefits terms.
For example, what are the costs of mismanaging soils (loss of carbon, decrease of food production, flash floods, dams siltation, irrigated fields salinisation …) and thus, what are the costs avoided when soils are managed in a sustainable way.

In socio-economic terms of global dimension, investments in soil improvement through runoff water control, adequate organic and mineral fertilization have proven and demonstrated dramatic impacts in small african farms(e.g.) .

Still they have been disregarded in these last decades, particularly in aid programmes for developping countries, neglecting the poorest of the farmers albeit they represent the vast majority.

Integrated research combining climatic, ecological, agricultural and socio-economical understanding is needed to foster a scientifically sound agro-ecological intensification of the use of soils. This the only way to enhance benefits from soils, from the local level (farms, particularly the small under-developed ones), through the regional (better management of fertilisers and pesticides at watersheds level) to the global one (overall impact on carbon and water cycles).

What is the feedback of ecosystems and in particular soils to changing climate?

Current models vastly disagree on the fate on the current terrestrial carbon sink, leading to large uncertainties regarding climate-carbon cycle feedback? Recent research indicates that soils contain more than 4 times as much carbon as the atmosphere (>3000 Pg), and soil carbon processes are clearly understudied.

What are the consequences of ground water reduction on agriculture?

I asked this question and I am concerned that population is growing therefor its food demand and more agriculture productivity means somehow losing soil strength and soil water (soil productivity). This may affect climate regionally. How to address such problem in next decade. If human want to survive than we have to address such question in next decade first rather than discussing water cycle and global warming as they are seems to be periodic.

what is the linkage between agricultural activities, biodiversity loss and sediment and nutrient fluxes into water systems and the overall impact of environmental degradation on the survival of humankind?

Agricultural production is a predominant activity of the majority of the rural poor in Sub-Saharan Africa. However, due to land degradation as a result of inappropriate farming techniques, there is continued loss of Biodiversity and soil fertility through soil and water erosion and these eroded materials (sediments and nutrient fluxes) end up choking water systems, this is evident in the network of rivers that feed into lake Victoria in East Africa.

How much land cover change (population growth) can be tolerated by ‘GAIA’ before irreversibilty takes its path?

Remember, soils and genes can be lost only once (irreversible). Soil losses reduce the planet’s capacity to store essential plant nutrients (all cations) and carbon (humus), both intimately linked to the presence of clay and, thus, intact soils. The number one driver behind this issue is growth in number of and consumption by humans.

How water is transformed globally between the ocean, land and the atmosphere?

Water is the most important nature factor for human life. It influences the human life directly. It is also the main driver of the climate. Although we do not have the global water budget information yet, but very close to have it. What we need is from space to monitor globally the atmosphere water content, the ocean salinity, the precipitation, the land soil moisture, the ground water run off, the polar ice melt, the underground water distribution and variations. We already have GRACE mission to monitoring the underground water distribution and variations, the polar ice melting, SMOS mission and SMAP mission will be launched soon to monitoring the land soil moisture and ocean salinity, FY3 and other weather satellites to monitoring the atmosphere water content, etc. However, the data are not integrately studied together and a more complete constelation of these kinds of satellites with higher tempo resolution are needed if we want a complete answer of this question. A global cooperation with participation of many governments like US, Europe, Russia, China, Japan and India is necessary!