NAIVASHA, Kenya — Two Kenyan fishers land their canoe on the edge of Lake Naivasha, tipping their silver catch on the grass under the eager eyes of their employer.

The meager haul of 20 bass — worth 800 shillings ($10) — is a far cry from what fishers working for Stanley Mungai would have netted a few years back.

Mungai, like many living near the shore, blames the environmental impact of 30 or so flower farms that have been set up around the lake in the past decade.

"We have tried to complain but nothing can be done because they contribute a lot to the Kenyan economy," said the 56-year-old fisher, referring to the flower farms housed in giant polythene greenhouses.

"The government should find a balance. We can't close the flower farms but we need to protect the fisherman."

Naivasha is the centre of Kenya's flower business, part of a horticultural industry that has expanded rapidly in recent years to earn some $63 million annually, one of the country's best sources of foreign exchange.

Growing carnations and roses to send by air freight to European markets provides many jobs, but locals say the farms aggravate some of the lake's biggest problems, contributing to pollution and falling water levels.

The flower farms in turn point to a wider set of problems, from a soaring lakeside population, to deforestation which reduces rainfall in its catchment area.

In Naivasha, the environmental stakes are particularly high. Nestling in the Rift Valley, the lake is an abundant source of wildlife with more than 400 bird species and giraffes, zebras, and antelopes grazing by its shores.

Tens of thousands of people rely on the fragile ecosystem to preserve their livelihoods in an environment that has increasingly come under threat.

Fish stocks falling

Falling fish catches are one of the most tangible signs of environmental damage.

Fishers blame the flower farms, accusing them of allowing pesticides and fertilizers to pollute the water reducing the fish stocks. They say the farms use powerful pumps that suck up both eggs and young fish. The level of the water is dropping.

Environmentalists say phosphates and nitrates nourish water hyacinth, a weed that spreads rapidly across the lake's surface, blocking out light needed by species living below and hindering the passage of fishing boats.

Flower farms say they are doing their best to reduce their impact on the lake, but point to other sources of pollution beyond their control.

The Lake Naivasha Riparian Association (LNRA), a non-governmental organization of lakeside land owners, blames pollution partly on the unplanned growth of Naivasha's population to 350,000 from about 50,000 just 20 years ago.

"The municipal council is one of the pollutants certainly," said LNRA Chairman Lord Andrew Enniskillen. "Their sewage works is not adequate for the size of the municipality as it has now become."

Fishers also point to shrinking water levels on the lake, saying flower farms are contributing to the problem by sucking out vast amounts to nourish their blooms. It takes about five liters to produce a single stem.

Oserian Flowers says it is doing its best to minimize its use of the lake by recycling water and reducing pesticide use, partly in response to demand from consumers for flowers grown in an environmentally friendly way.

Degraded catchment areas

Demand for water from flower growers is compounded by another problem facing much of Kenya — deforestation.

Communities are cutting down trees for farms or firewood, removing a key component of the environment that helps produce rain feeding the lake.

For peasant farmers, falling water levels may at first seem a blessing that allows them to increase the amount of land under cultivation — even if environmentalists say the long-term effect could be dire.

"As soon as that bit dries up, we follow it," said Joseph Kamau, standing on a patch where he grows beans.

Like many poor farmers and fishers, Kamau says responsibility for caring for the lake should rest with the flower farms rather than poverty-stricken families.

"You can't tell a hungry man to care for the lake," he said. "Enable him to produce his food first if you hope to get him to care for his surroundings."