Environmental services group RPS Group's half yearly pre-tax profit fell marginally, partly hurt by severe weather conditions in Australia and the political turmoil in the Middle East and North Africa, sending its shares lower.The company's move to raise interim dividend by 15% also failed to inspire investors. For the six months ended 30 June, the company's revenue rose 11.3% to £251.5m, up from £226m in the corresponding period last year. Profit before taxation, for the period, was nearly flat at £23.5m, compared with £23.4m, a year earlier. Looking forward, "The second half should see an improved performance, as the impact of these exceptional events reduces, with continued growth from our energy and environmental management activities, including a larger contribution from the three acquisitions made in the first half. This should enable market expectations for 2011 to be achieved," chairman Brook Land said.In the first half, RPS acquired Evans-Hamilton, which provides oceanographic consulting services. It bought Nautilus and Nautilus Word in March and acquired 50% of Australia's Terranean Mapping Technologies.Shares of the company slid 0.3% to 236.6p in late morning trading in London. Its shares have risen 2.7% since the beginning of this year.AR