Can marginal seas account for the missing CO2 and is the marginal sea sink affected by human activities on land?

Current estimate of CO2 uptake by the oceans by and large ignored marginal seas and continental shelves. Preliminary investigations indicate that these areas are a larger sink of CO2 than open oceans on the per area basis. If proven, this sink may be as large as 25% of the oceanic sink. Human activities on land are affecting this sink via construction of dams, increasing nutrient discharge into the continental shelves, etc. Global synthesis, however, is nonexistent because of insufficient data.

How much longer are extractive land uses sustainable? The fate of nutrients.

Searching harvest, export, cycle, biogeochemical, mineral on this site (Aug7): no questions were found addressing the continuous export of nutrients. The human enterprise today is based on consuming natural resources (NR) in highly concentrated places, like cities. Much valuable nutrients end up in waters, dumps or burns. Areas of NR production tend to be wide spread and at large distance from site of use. Fluxes of nutrients are thus frequently one-way: site of production-cities-oceans.

The remedy: fertilizers. The ABC for gardeners and farmers (actually NPK). However, fertilizing has become necessary EVEN FOR EXTENSIVE livestock production, or forest harvesting. The rate of change may be slower, but soil reserves have been depleted in such systems, and fertilizing is necessary. Besides NPK, in some situations plants need other elements like Ca, Mg, S, Bo. HOWEVER, livestock, wildlife and humans need some additional trace elements which are not needed by plants, or in much lesser quantity: THESE are practically never placed in fertilizers.

Thus, some elements are being constantly removed and exported, but without replacement. If soil conditions do not replenish them, then soil reserves become depleted over time. Continuous NR extraction in semi-natural extensive system without fertilizer will thus deplete soils and affect wildlife and ecosystems. Not only is fertilizer application at the landscape level expensive, but some key nutrients are becoming in short supply, beside being practically non-renewable. To mention is phosphorous (2009 The story of phosphorus: Global food security and food for thought. Global Environ Change 19:292). Oil peak? The current discussion about peak phosphorous is also eminent. Other nutrients are also in discussion, but more in technical circles, and far from mainstream.

Biomass export, biogeochemical nutrient cycles affect various future scenarios:
- nutrient competition between growing for food versus bio-energy
- competition of nutrients used for food versus alternative energy systems (e.g. photovoltaic, batteries)
- nutrient limitations in extensive systems (with little opportunity for remedy), and effects on ecosystem service

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.