Attempting restoration of wet tropical forests in Costa Rica
A. Carl Leopold1, Richard Andrus2, Arno Finkeldey3, and David Knowles4
The Tropical Forestry Initiative, Box 285, Ithaca NY 14851

Jan 14 2000

Abstract
In southwestern Costa Rica, where the wet tropical forests have been seriously degraded to make way for pasture, many pasturelands are now idle or are coming up in scrub. Plantations of exotic species of trees in monocultures are the usual methods at obtaining forest cover. This report describes progress in an effort to show that restoration of wet native forest can be stimulated by planting mixed stands of native hardwoods. On a private reserve of 145 ha of abandoned pastureland, mixed stands have been established, involving up to 41 native species in the period since 1993. Sunloving species are growing as much as 3.1 m/year in height, and have exceeded 10 cm dbh in 5 years. Mixed stands of indigenous species are proposed as an alternative to monocultures, providing a possible source of income for small farmers, stabilizing the soil, and stimulating the restoration of biodiversity.

Introduction
It is estimated that tropical forests originally covered between 96 and 99% of the land in Costa Rica. This was an enormous resource in terms of useful materials, benefits through stabilization of climate, and supportive biodiversity. In recent decades, an estimated 90% of the original forests have been destroyed, and some 46% of the total land has been converted into cattle pasture (Koll 1995, Bryant et al. 1997, Mattoon 1998). Deforestation continues at an estimated rate of 3.1% per year. Because much of the original timber-producing forests are gone, Costa Rica is now experiencing a negative balance of trade in timber, and it imports more than $500 million of wood per year (Bryant et al. 1997).

Changes in the international market for lean beef, and deterioration of soils under grazing conditions, have caused many farmers to decrease or abandon cattle production. Consequently in some areas, scrub growth has begun, and there is a great need for restoration forestry. It is an appropriate time to consider the options for real reforestation.

The problem of forest restoration
A problem of major importance, then, is how to foster forest recovery. Plantation forestry is being utilized world-wide on formerly forested tropical land. In most instances, this has involved the planting of monocultures, usually of exotic tree species which have rapid growth rates. In Costa Rica, such plantations have mostly utilized such exotic species as Gmelina arborea (Gmelina), Eucalyptus deglupta (Eucalyptus), or Tectona grandis (Teak), the former two being used for chipping and paper production, the latter for flooring. Monoculture plantations of exotic species may provide a cash crop, but they have come under considerable criticism in recent years for their tendency toward long-term ecosystem decline (Maser 1994), depletions of water tables, and the need to employ pesticide use (Carrere and Lohman 1996). Such monocultures are ordinarily established by large landholders, and are less appropriate for local farmers, as they usually require considerable technical management; they provide essentially no return to the local farmers. The sustainability of monocultures has been questioned from both economic and ecological viewpoints (Mattoon 1998), and the large-scale production of wood-chip biomass is considered a poor contribution to the need for sustainable development (Carrere and Lohmann 1996).

The use of native species in reforestation work has been proposed by numerous authors (Nichols and Gonzalez 1992, Richter and Calvo 1993, Parrotta 1993, Butterfield and Fisher 1994, Calvo et al. 1997, Haggar et al. 1997). And probable extra benefits of native species in mixed stands have been pointed out many times (Matthews 1989, Panayotou and Ashton 1992, Lamb and Lawrence 1993, Brown and Lugo 1994, Ball et al. 1995, Keenan et al. 1995, Knowles and Parrotta 1995, Montagnini et al. 1995, Parrotta et al. 1997). Nevertheless, there are singularly few data on the performance of mixed stands in Latin America.

New concepts of plantation
Two changes in assessment of the reforestation problem have been offered in the past decade: (1) plantation of native tree species in monocultures has been given some considerable attention (Nichols and Gonzalez 1992, Butterfield and Fisher 1994), and (2) the concept of using plantations as a "catalytic technique" to "jump-start" succession towards native forests has been demonstrated by Lugo (1997) and Parrotta et al. (1997).

The logic of the Nichols/Butterfield scheme is simply that native species can provide wood which is of higher value than the chips obtained from fast-growing exotic trees. The logic of the Lugo scheme is that the planting of rapidly-growing species can drastically modify the microclimate at the ground level, markedly improving conditions for the natural establishment of native tree seedlings. The modification of the microclimate can stimulate succession towards the native tropical forests. The effectiveness of such a jump-start towards tropical forest development has been clearly documented (Powers et al.1997). We are attempting to measure the success of planting mixed stands of native species for forest restoration in the pasturelands of Costa Rica.