I would suggest that the issue of forest ecosystem loss is not a simple choice between forest preservation or human use. As long as humans inhabit the planet (and there will be more and more of us) the fundamental driver of ecosystem change will be the value that people attach to alternative land uses. One of the best approaches to preserving forest cover is to insure that there is significant value attached to it--through active management and sustainable harvest, recreational use, non-timber forest products, or other monetized ecosystem services. Bioenergy can be a positive factor in maintaining forests by providing market values for residues and thinning. The great challenge for forest science is to understand how we can use forests intelligently while maintaining ecological function.

Forests are lost/converted in the tropics (see my paper from Bolivia) at a rate of 1-2% per year ; in the temperate and boreal zones forest are expanding at approximately the same rate (see my paper from Italy). Economic development will do the trick. Agriculture will be concentrated on the better/flatter lands and marginal lands left to natural reforestation.

Just to add a twist to Hein's response. I fully support the idea that free markets drive determination of land use to a large degree. This can be bad in several ways--the market may not (probably doesn't) fully incorporate all costs/benefits. How does the value of wildlife habitat factor into a private landowner's decision against clearing the forest and getting income from crops? When the benefits accrue to a private landowner but the costs are borne by society--how does a totally free market effectively allocate land use?

My point was simply that increasing the perceived value of forest land as forest is one of the most significant approaches to preserving forest and preventing ecosystem loss. It is easier to do that by developing tangible products such as bioenergy compared to trying to establish market values for things like esthetics or clean water. None of those values matter if the alternative land use has clear economic gain (urban land conversion for example). In such cases public policy (zoning, for example) is needed to constrain land-use choice.

My finding in Bolivia was that zoning (e.g. as protected area) may be ineffective; locally present owners are required to protected their forest resources.

I endorse above view points. One of the solution is to mobilize local communities as govt alone can't do every thing.

Green roofs are best options in urban areas to conserve the plant ecosystems. Selection of most suitable growing medium is must in this regard. I would like to recommend the following paper which provides comprehensive idea in this aspect:

Preprint Analysis of Physical and Chemical Properties of Alternative ...