Should we be constructing artificial reefs as havens for harried marine life? Why does no-one talk about cement when discussing climate change yet it is one of the biggest emitters of carbon dioxide? And just how much carbon dioxide is there in the atmosphere and can human activity really effect it? Also, how well is the message about environmental degradation being transmitted and why do larger animals live longer than small ones? On the panel are marine biologist Dr Helen Scales, Professor Andrew Watkinson, Director of Living With Environmental Change, and Professor Philip Stott, environmental scientist at the University of London. As always we want to hear your comments on the topics discussed and any questions you might want to put to future programmes. House Martins. We want to hear your observations of House Martins; have they returned this year and when, and have they bred successfully? Finally, Home Planet will be at the British Birdwatching Fair at Rutland Water to record a programme on the evening of Friday 21 August. Listeners are invited to come to the recording, and if you want to ask a question, please let the programme know in advance by clicking on the Contact Us link above.