This is a new ditched enclosure recently found in Google (by Tiago do Pereiro) in North Alentejo. In my inventory is number 63 in Portugal. It is quite visible in the image of 2006.
In March 2009 the situation was as follow: a change in the agricultural use of the soil was threatening the enclosure.
And just a few months later, in August 2009, the site was affected by the new plantation. It looks like a vineyard and, if so, the impact was strong, for ploughing for vineyards is deep.
This happens because, in Portugal, impact assessment legislation is not applied to large agricultural programs with deep impact in the soil. Now, the site is inaccessible, even for geophysics, and probably suffered a strong destructive effect. And it seems relatively small (70m diameter), so if it was discovered in time through an archaeological preliminary prospection, it could became a protected area without a significant economic impact for the agricultural project, and could be used for other cultures with less effects in the ground.