Impax, the asset manager focused on the environmental markets sector, saw plenty of green shoots of recovery in the first half of its financial year.Assets under management (AuM) rose by 30% to £2,362m at the end of March from £1,823m at the end of September. At the end of April, AuM had risen further still, to £2,372m."Developments of the past few months, particularly unrest in the Middle East, damage to the Fukushima nuclear reactors and China's adoption of a new Five Year Plan, have significantly strengthened the prospects for investors in environmental markets," claimed chief executive, Ian Simm.The performance of market indices back up Simm's claim. In the period covered by the group's interim results, the FTSE Environmental Opportunities All Share Index rose by 17.5%, while over the same period the MSCI World Index rose 12.2%.It was not all beer and skittles for the sector, however, with renewable energy stocks continuing to suffer from over-capacity and investor concerns over government subsidies.Impax's revenue in the six months to 31 March surged to £9.86m from £6.31m at the interim stage last year, while profit before tax jumped to £2.0m from £1.67m, despite an exceptional charge of £1.53m related to a change in the taxation rules applicable to the company's long term incentive scheme.Diluted earnings per share rose 15% to 1.27p. The board does not propose an interim dividend for half year.--jh