Freshwater habitats

The situation today

The county of Essex is bounded by rivers, with the Stour to the north, the Lea and its tributary the Stort to the west, and the Thames in the south. Within this boundary there are several major rivers running eastwards to the sea - the Colne, Blackwater, Crouch and Roach, each with many miles of associated tributaries.

Historically rivers have been the single most important factor in determining land use in the valleys, winter flooding enriching with nutrients the meadows adjacent to watercourses. Water power has also been harnessed for industry and has acted as a nucleus for many towns and villages. Rivers and streams also provide a diverse and valuable habitat for many animals and plants.

Much of the natural flow of our rivers has been lost through modification and straightening of channels, and due to abstraction for water supply and irrigation. Low flows are likely to be an increasing problem if global warming ensues and many plants and animals may disappear due to the direct effects of absence of water or indirect effects of concentration of pollutants. The modification of flows has also resulted through drainage of land and conversion to arable, and building of housing and industry within flood plains. The alteration of water-courses has led to a reduction in bankside habitat, a loss of reedbeds and marshes and changing patterns in the erosion and deposition of sediments in the river bed.

Rivers have always been convenient places to get rid of wastes. In past times such wastes were largely organic and hence biodegradable, while human populations were small. Since the 1950S there has been a great increase in urbanisation and industrialisation in the county, while agriculture has intensified. All of the sewage entering our rivers is treated but in some rivers the loading is such as to reduce the biological quality of the ecosystem. Sewage is also a major source of the high phosphate levels in many of our rivers.

Fertilizer additions to farmland add phosphates but are especially responsible for the high nitrate levels in our rivers. These nutrients cause eutrophication, stimulating plant and algal growth and causing serious imbalances in aquatic systems. Agriculture is also a source of pesticide runoff into freshwaters, many of which penetrate into groundwaters, an important source of our own water supply.

Industry adds many chemicals to rivers. A number of the freshwater contaminants bioaccumulate in food chains and are known to affect male and female fertility, to impair the endocrine and immune systems and to cause cancers in living organisms.

The National Rivers Authority classes most stretches of Essex rivers as of good or fair quality but there are substantial stretches of the Wid and Crouch which are of poor quality and the Higham Brook is of bad quality. These assessments of water quality are based largely on criteria of organic pollution and do not consider plant growth nutrients or toxic chemicals. Current monitoring and water quality standards are totally inadequate for protecting the wildlife of rivers.

The Wildlife of our Waterways

Pollution and river management have led to the loss of the otter in Essex and a decline in numbers of kingfishers, dragonflies and damselflies and water plants. Nevertheless many stretches of river still hold diverse communities of plants and animals typical of lowland watercourses and, with sensitive management and pollution control, rivers can recover quickly from the ravages of the past.

Large volumes of water are abstracted to our water supply reservoirs. Abberton Reservoir is of international importance for its waterfowl populations while Hanningfield and the reservoirs along the Lea are also of significance.

Abberton and Walthamstow Reservoirs have the only tree nesting colonies of cormorants in this country and both are expanding, while Walthamstow Reservoir has by far the largest heronry in the county. Essex Wildlife Trust has reserves at both Abberton and Hanningfield, with a modern and very popular visitor centre at the former.

In days past ponds were an important feature of village, farm and wood, as watering places for horses and livestock. With the loss of the working horse and the switch to a largely arable agriculture in Essex many ponds have been filled in and even more have been unmanaged for many years. They have also been used to dump old machinery and empty containers of biocides. The majority of these rich little ecosystems are a shadow of their former self but with increased awareness of their value and sensitive management they can be readily restored.

Along with this decline in the country pond there has been a tremendous growth in the garden pond. Most of the county's frogs and newts now live in garden ponds while they are also inhabited by dragonflies and damselflies, especially the blue-tailed and common blue damselflies, southern hawker, broad-bodied chaser and common darter dragonflies. Although populations in individual ponds are generally small, the fact that there are many thousands of garden ponds in the county makes them of considerable significance to conservation.

Over the last decade there has been a substantial increase in the number of farm reservoirs in the county, largely replacing country ponds in importance as freshwater wildlife habitats. The majority of reservoirs have been designed without consideration of wildlife but nature, over time, has a habit of softening the raw edges of these waterbodies. The majority are used by tufted duck and mallard on a regular basis, with other wildfowl occasional. Most farm reservoirs in Tendring have a pair of dabchicks, while many have breeding mute swans. Regular watching reveals the diversity of birds which pass through these sites in the course of a year, including rarities such as osprey.

They also hold water plants and dragonflies. However they have never been systematically surveyed and they may prove to be of greater significance than we currently believe. Some would make ideal parish nature reserves.

Another recent development has been the increasing use of reedbeds as natural reed-bed filtration systems for the treatment of household and light industrial sewage. Adopting and optimising the wildlife opportunities of such water storage and treatment facilities should be encouraged wherever possible.

Essex has few natural lakes but many of our larger country houses have lakes which were created in earlier centuries as part of the overall landscape design of their parks. Again we have little systematic knowledge of their value as wildlife habitats. The river valleys of Essex have rich reserves of gravel which have been and are still extensively exploited. The water-filled pits which are left can develop into rich wildlife sites and some, such as Fingringhoe are Essex Wildlife Trust reserves. Unfortunately there appears to be no overall strategy for the after-use of worked-out pits and no specific consideration of the wildlife value of these sites.

In conclusion pollution and excessive river management have led to a deterioration of the wildlife value of our watercourses over the past fifty years, while there has been a great loss of farm ponds over the same period. in contrast new water supply reservoirs have become major wildlife sites, while there has been a tremendous growth in the number of gravel pits, farm reservoirs and garden ponds. These will have significant wildlife interest and potential for further enhancement.

Targets for 2000

• Maintain and protect those freshwater habitats that exist today and support the protective measures that are available (SSSI, NNR, LNR, ESA, SPA designations).
• Improve the management of our rivers, ponds and lakes for wildlife.
• Insist on water quality objectives which include the requirements of wildlife and improve water quality to meet these objectives.
• Encourage and promote the creation of new freshwater habitats in the county.
• Carry out systematic surveys of farm reservoirs to assess their importance and potential for wildlife conservation.
• Promote the concept of river corridor management and ensure that wildlife sites are fully represented in catchment management plants.
• Aim to increase the quality of bankside habitat in the county by 10% and associated riverine habitat (marsh, fen, wet woodland) by 15%.
• Promote wildlife as indicators of the wholesomeness of our own water supplies.

Achieving the Freshwater Aims

• Establish a network of riverine and freshwater SINCs co-ordinating with the Environment Agency to achieve this target.
• Use existing schemes (ESA and Farm Ponds schemes) to improve the management of bankside habitat and increase the amount of such habitat.
• Ensure that Essex Wildlife Trust and other wildlife organisations have a full input into Catchment Management Plans and ensure that such plan are developed.
• Work with both the planning authorities and abstraction companies to ensure that there is a flexible, co-ordinated plan for the after-use of mineral workings which fully takes into account their value for wildlife.