As shown by a study conducted in the DRC, the links between drought and deforestation depend in particular on the season in which the phenomenon occurs.
Extreme climatic events, in particular droughts, have very significant effects on populations of southern countries, particularly within the agricultural and livestock sectors: lower yields, increased livestock mortality, loss of ecosystem services, etc.
The attribution of these events to climate change is a complex and still uncertain science, so much so that it is difficult today to generalize the idea that the occurrence of drought increases with climate change. However, this link is established in certain regions of the world, such as North Africa, West Africa or South Africa.
Faced with these events, farmers have recourse to a large number of coping strategies. First of all, we can distinguish the adaptations long-term, to anticipate the possible occurrence of future droughts; and short-term adaptations, to respond to droughts once they have occurred.
We can also distinguish adaptation practices that take place in the agricultural sector, such as the diversification of crops, the sale of livestock, agroforestry or the use of seeds that are more resistant to water stress; and practices outside the agricultural sector, such as the collection of non-timber products from the forests, internal or external migrations, or recourse to loans.
These different practices are likely to have implications in terms of land use. Some can be described as intensive in terms of land use, that is to say that they risk encouraging agricultural expansion; while others will be more land efficient.
Thus, bearing in mind that agricultural expansion is the main driver of tropical deforestation, adaptation can, depending on the context and the characteristics of the farmers, increase or reduce deforestation, which is a major cause of climate change and loss of biodiversity.
When drought accentuates deforestation
The analysis of the links between droughts and deforestation is therefore an emerging study theme, allowing the identification of possible situations of maladjustment ; that is, adaptive behaviors that aggravate environmental degradation.
On average, short-term adaptation practices to droughts would therefore be rather intensive in land use and would lead to more deforestation.
However, these studies also show sources of heterogeneity in these impacts: the positive link between droughts and deforestation is not uniform.
Maize and cassava in the DRC
To this end, we have considered the agricultural seasons of the two most produced commodities in the country: maize, where the episodes of planting, growth and harvest are distinguished; and cassava, where planting and harvesting episodes are distinguished.
For each episode, we couple rainfall weather data monthly, a drought being considered here as a significant rainfall deficit compared to the average over a given period, with data on loss of forest cover, our deforestation indicator.
Based on an annual statistical analysis between 2000 and 2020, we seek to observe significant links between rainfall accumulation deficits and the level of deforestation.
The importance of seasonality
Our results tend to show that seasonality plays an important role in the links between drought and deforestation. If we consider maize, the occurrence of drought in a given year lowers deforestation if it takes place during planting and growth episodes, while it increases it during harvest episodes. By focusing on cassava, we find that only droughts occurring during planting periods push deforestation upwards.
We also observe that past droughts can affect deforestation. Thus, droughts that have occurred in past years during maize growth episodes tend to reduce deforestation. This result can be interpreted as a long-term adaptation behavior of farmers.
The droughts of past years, having had a negative impact on maize yields, can then influence farmers' expectations and thus modify their choice of cultivating new land.
Distance to cities, role of protection
We are also looking to what extent other factors influence this link between drought and deforestation. We first take the case of the access time to the nearest densely populated area: this distance is an indicator of transport costs to the main markets, and thus represents the way in which farmers can be integrated into the rest of the the economy.
This proximity to markets tends to accentuate the impacts on deforestation, whether positive or negative. This result suggests that proximity facilitates access to coping strategies, and therefore increases their use. This is the case both for strategies that are intense in land use, during maize harvest times; and for strategies that save land use, during maize growth episodes.
Finally, we consider the role of protected areas, whose objective is to participate in the conservation of ecosystems. We can see that the presence of protected areas tends to reduce the impact of droughts on deforestation. Thus, in the event of drought during maize growth episodes, protected areas reduce the positive impact on deforestation.
Conversely, and more surprisingly, the presence of protected areas tends to compensate for the negative effect of droughts on deforestation, when these occur during periods of maize growth.
Shocks, adaptation and environmental degradation
All in all, we can see that it is important to take into consideration cases of mal-adaptation, when responses to meteorological shocks lead to adaptation behaviors that reinforce climate change and biodiversity loss by accentuating the expansion cultivated land.
As such, it seems very important to succeed in reconciling better resilience of vulnerable populations and better conservation of ecosystems. This point is all the more important when we know the role of these ecosystems in the climate regulation and the resources they bring to people.