DECC
Chris Huhne MP for Eastleigh
Gregory Barker MP for Bexhill and Battle
Charles Hendry MP for Wealden

Department for Transport
Philip Hammond, MP for Runnymede and Weybridge: responsible for transport security - including Transec, high speed rail, transport strategy

Defra
Caroline Spelman MP for Meriden
James Paice MP for South East Cambridgeshire
Richard Benyon MP for Newbury
Lord Henley (Parliamentary Under-Secretary)
Defra is the only department which has so far published information about which minister is responsible for which policy area.

To make it easier for you, we're listing these below in alphabetical order.
If and when the other departments do the same thing we will add that to this list:

Agricultural Wages Jim Paice
Agriculture and forestry carbon budgets Jim Paice
Air quality Lord Henley
All departmental business in the Lords Lord Henley
Animal health (including endemic and exotic diseases) Jim Paice
Apprenticeships Richard Benyon
Bee health Lord Henley
Better regulation Jim Paice
Biodiversity Richard Benyon
biodiversity Caroline Spelman
Biofuels Lord Henley
CAP reform, Caroline Spelman
Chemicals and pesticides (inc CBRN) Lord Henley
Climate change Caroline Spelman
Climate change & adaptation Lord Henley
Climate change & Defra's interest in mitigation and overall carbon budgets lead Lord Henley
Coastal and wider access, countryside and rights of way Richard Benyon
Coastal erosion Richard Benyon
Dangerous Dogs Lord Henley
Defra overall responsibility Caroline Spelman
Departmental administration Richard Benyon
Deputising for the Secretary of State at EU Agriculture Council Jim Paice
Deputising for the Secretary of State at EU Environment Council Lord Henley
Ecosystem services Richard Benyon
Emergencies Caroline Spelman
Environment Agency Caroline Spelman
Environmental regulation Lord Henley
EU and international relations Caroline Spelman
EU Fisheries Council Richard Benyon
Farming Jim Paice
Fisheries, including CFP Richard Benyon
Flooding and water (including Nitrates) Richard Benyon
Food Jim Paice
Forestry (including Forestry Commission) Jim Paice
Gangmasters Licensing Jim Paice
Global monitoring of environmental security (GMES) Lord Henley
GMOs Lord Henley
Hunting and shooting Jim Paice
Inland waterways (including British Waterways) Richard Benyon
JNCC Richard Benyon
Kew Gardens Lord Henley
Land management (including commons and contaminated land) and soil Richard Benyon
Legislative programme Caroline Spelman
Local and regional government Lord Henley
Local environmental quality, including noise Lord Henley
Localism and third sector Lord Henley
Marine and Coastal Access Act implementation Richard Benyon
Marine Environment Richard Benyon
Marine Management Organisation Richard Benyon
Nanotechnology Lord Henley
National parks and areas of outstanding natural beauty Richard Benyon
Natural England Caroline Spelman
Natural environment Richard Benyon
Plant health Lord Henley
RDPE Jim Paice
Responsibility and cost-sharing Jim Paice
Royal Commission on Environmental Pollution Lord Henley
Rural Affairs Richard Benyon
Science, evidence and research Lord Henley
Seasonal Agricultural Workers Scheme (SAWS) Jim Paice
Single Payments Scheme Jim Paice
Strategy, budget and finances Caroline Spelman
Sustainable Consumption and Production Lord Henley
Sustainable development Lord Henley
Waste and recycling Lord Henley
Welfare of companion and wild animals Lord Henley
Welfare of farm animals Jim Paice
Wildlife Richard Benyon