Vegetation in Rwanda

Lessons

Senior 4 · Geography

Vegetation in Rwanda

3 lessons

Lesson 1 of 3

Types of Vegetation and the Distribution of Natural Forests

25 min

More than half of the "forest" was planted

In 2019 the Ministry of Environment mapped every patch of trees in Rwanda. Figure 1 shows the result. Before reading on, use it to answer two questions: which type of forest covers the most land, and what fraction of all the forest was planted by people?

Figure 1. Forest area by type, 2019. Plantations (orange) are planted; the other four bars (green) are natural vegetation. Data: Rwanda Forest Cover Mapping, Ministry of Environment, 2019, as reported by REMA (2021).

Plantations alone cover 387,425 ha, more than all the natural types together. The natural rainforest that most people picture when they hear "Rwandan forest" is less than a fifth of the total.

Definition

Vegetation: the plant cover of an area, taken as a whole (trees, shrubs, grasses and herbs). Example: the papyrus that covers the Rugezi marsh.

Natural vegetation: plant cover that has grown without being planted by people, adjusted to the local climate, soil and relief. Example: the montane rainforest of Nyungwe.

Planted (artificial) vegetation: plant cover established by people: forest plantations, woodlots, agroforestry trees, crops and planted pasture. Example: eucalyptus woodlots on the central plateau.

Forest cover: the percentage of a country's land under forest. Rwanda's official definition counts groups of trees on as little as 25 m² of land, so it includes small woodlots (REMA, 2021).

Worked example 1: which area is "30.4%" measured against?

Problem. REMA (2021) says forests occupy "about 30.4 percent of the total land area", and Figure 1 adds up to 724,694 ha. NISR gives Rwanda's total area as 26,338 km² and its land area as 24,210 km². Which area gives 30.4%?

Solution. Since $1\ \text{km}^2 = 100\ \text{ha}$ , the forest area is $7\,246.94\ \text{km}^2$ .

\frac{7\,246.94}{26\,338} \times 100 = 27.5\% \qquad \frac{7\,246.94}{24\,210} \times 100 = 29.9\%

Neither gives 30.4%. Work backwards instead:

\text{area used} = \frac{7\,246.94}{0.304} = 23\,839\ \text{km}^2

This is the figure of 23,835 km² of "national dry lands" that REMA's 2009 report uses: land without the lakes, rivers and the swamps. Conclusion: a percentage is only meaningful when you know its denominator. Always say "30.4% of dry land (2019)".

The natural vegetation types

Rwanda's plant life changes from west to east. REMA describes habitats "ranging from afro-montane ecosystems in the northern and western regions to lowland forests, savannah woodlands and savannah grasslands in the southern and eastern regions" (REMA, 2009). Rwanda has about 3,000 species of vascular plants.

Type	Where it is found	Typical plants and features
Montane (mountain) rainforest	Congo–Nile Ridge: Nyungwe, Cyamudongo, Gishwati, Mukura; lower slopes of the Virunga volcanoes	Tall evergreen trees in several layers, tree ferns, lianas, epiphytes such as orchids; 148 orchid species in Nyungwe alone
Bamboo forest	Volcanoes National Park; parts of Nyungwe	Dense stands of mountain bamboo, one woody grass species forming the canopy
Afro-alpine and sub-alpine vegetation	Upper slopes and summits of the Virunga volcanoes	Giant lobelias and giant groundsels (Dendrosenecio), then grassland near the highest summits
Wooded savannah and shrub savannah	East: Akagera National Park, Bugesera, Gisaka, Umutara	Grasses with scattered, often thorny trees: Acacia senegal, A. sieberiana, Combretum
Grass savannah	Akagera National Park and parts of the east	Tall grasses dominated by Themeda triandra and Hyparrhenia
Gallery (riverine) forest	Along rivers and lakes of the Akagera valley	Strips of tall trees fed by groundwater (Albizia, Cordia africana, Ficus); about 163 ha in the Akagera complex
Swamp (wetland) vegetation	Rugezi, Akanyaru, Nyabarongo and Akagera valleys	Mainly papyrus (Cyperus papyrus), reeds and sedges rooted in waterlogged soil

Sources: REMA (2009), citing national biodiversity studies; REMA (2021).

Planted vegetation

The first plantations in Rwanda were made between 1920 and 1948, when eucalyptus was introduced. Pines, Callitris, Grevillea robusta, Cedrela and cypress followed (REMA, 2009). Today plantations are dominated by several eucalyptus species, which grow fast, sprout again after cutting and supply poles, firewood and charcoal. Planted vegetation also includes:

agroforestry trees on farms and along anti-erosion ditches (Grevillea, Calliandra, Leucaena);
indigenous trees planted around homesteads, such as Ficus thonningii, Erythrina abyssinica and Euphorbia tirucalli;
crops and planted pasture, which now cover most of the country's hills.

Where the natural forests survive

Figure 2. Natural vegetation in Rwanda's protected areas. Drawn by Ganzaa from OpenStreetMap park, forest and wetland outlines, geoBoundaries district boundaries and Natural Earth.

Read the map with three questions in mind.

Where? Montane forest survives only as islands on the high ground of the west and north-west: one large block (Nyungwe), three small ones (Cyamudongo, Gishwati, Mukura) and the forest belt of the volcanoes. Savannah survives in the far east, mainly inside Akagera National Park.
Why there? These are the steepest, coldest, wettest or driest lands: the hardest to farm. They were protected early: Gishwati was made a forest reserve in 1933 (REMA, 2021).
What is between them? Farmland, pasture and plantations. The pattern is the result of people, not of climate alone.

Protected area	Forest area (ha)	Vegetation
Nyungwe National Park	111,561	Montane tropical rainforest
Volcanoes National Park	16,000	Montane tropical rainforest
Akagera National Park	113,160	Shrub land and savannah
Gishwati-Mukura National Park	4,520	Montane tropical rainforest
107 forest reserves (e.g. Busaga, Sanza, Iwawa, Makera)	37,886	Montane forest, shrubland, savannah woodland

Source: REMA (2021), Table 4-3. The figures are areas of forest and woodland, not the legal areas of the parks.

Worked example 2: why are the most forested districts all in the south-west?

Data (MoE 2019, in REMA 2021). Nyaruguru has 55,759 ha of forest, which is 55% of its land. Rusizi 53%, Nyamagabe 50% and Nyamasheke 48% follow.

Step 1: check the figure. If 55,759 ha is 55% of Nyaruguru, the district's land area is

\frac{55\,759}{0.55} = 101\,380\ \text{ha} \approx 1\,014\ \text{km}^2,

a sensible size for a Rwandan district, so the percentage is consistent.

Step 2: look at the map. All four districts share the Nyungwe forest block (Figure 2). Their high forest cover comes mainly from one protected rainforest, plus tea-estate woodlots.

Step 3: compare the east. Kayonza (45%) and Gatsibo (43%) are also highly wooded, but by savannah woodland around Akagera. Same statistic, different vegetation: always ask which type of forest a percentage counts.

Warning

Do not call all trees "forest". A eucalyptus woodlot, an acacia savannah and the Nyungwe rainforest all count in the national forest statistics, but they are different vegetation types with very different value for wildlife and water. In an exam answer, name the type and give an example place.

REB elearning: "S4 Geography, Unit 7: Vegetation in Rwanda". A Rwanda Basic Education Board lesson on this unit. As you watch, list each vegetation type it names and add one place from Figure 2 for each.

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Practice

Distinguish natural from planted vegetation, with one Rwandan example of each.
Name four natural vegetation types found in Rwanda and one place where each occurs.
Use Figure 1 to calculate the percentage of Rwanda's forest area that is natural vegetation of any kind.
Explain why the natural forests of Rwanda survive mainly on the Congo–Nile Ridge and the volcanoes.
Kayonza has 80,545 ha of savannah woodland, which is 45% of its land. Calculate the district's land area in km².
Describe two differences between the vegetation of Cyamudongo and of Ibanda-Makera, using the photos.
"Rwanda's forest cover rose to 30.4%, so its natural forests are safe." Evaluate this statement.

Show answersHide answers

Natural vegetation grows without being planted (e.g. papyrus in Rugezi, rainforest in Nyungwe); planted vegetation is established by people (e.g. eucalyptus woodlots, tea, agroforestry trees).
Any four, e.g. montane rainforest (Nyungwe), bamboo (Volcanoes NP), wooded savannah (Akagera), swamp vegetation (Rugezi), gallery forest (Akagera valley), afro-alpine (volcano summits).
$387\,425$ ha are plantations, so natural $= 724\,694 - 387\,425 = 337\,269$ ha; $\frac{337\,269}{724\,694} \times 100 = 46.5\%$ .
These lands are steep, high, cold and very wet, so they were harder to farm; they were also protected early as reserves and parks, while gentler land elsewhere was cleared for farming.
$\frac{80\,545}{0.45} = 178\,989$ ha $\approx 1\,790\ \text{km}^2$ .
Cyamudongo: closed, continuous canopy of tall trees on steep hills, with tea and woodlots below. Ibanda-Makera: open grassland with scattered broad-crowned trees on gentler slopes near a swampy valley.
Only partly true. More than half of the forest is plantations (Figure 1), and the rise came mostly from planting and agroforestry. Natural forest is a smaller share and can still be lost even while the total rises, so the total alone does not show that natural forests are safe.

Quick check

According to the 2019 forest mapping, which type covered the largest area of Rwanda's forest?

Key points

In 2019 Rwanda had about 724,700 ha of forest: 53.5% plantations, 22.3% wooded savannah, 18.1% natural mountain rainforest, 6.1% shrubs, 0.1% bamboo (MoE 2019, in REMA 2021).
Natural types: montane rainforest, bamboo, afro-alpine, wooded and grass savannah, gallery forest, swamp vegetation. Planted: plantations, woodlots, agroforestry, crops, pasture.
Natural forests survive as islands in protected areas: Nyungwe, Cyamudongo, Gishwati-Mukura and the volcanoes in the west; savannah in Akagera in the east.
The 30.4% forest cover is measured against dry land (about 23,835 km²); always state the denominator and the year.

Sources and credits

Sources: Rwanda State of Environment and Outlook Report 2021, Rwanda Environment Management Authority (REMA), 2021, reporting the Ministry of Environment's Rwanda Forest Cover Mapping, 2019 (forest types, district and protected-area figures, definition of forest); Rwanda State of Environment and Outlook Report, REMA, 2009 (vegetation types, plant species, history of plantations, dry-land area); Volcanoes National Park, Wikipedia contributors, CC BY-SA 4.0, adapted by Ganzaa (afro-alpine plants); Statistical Yearbook 2019, NISR (total and land area).

Figure 1 was drawn by Ganzaa from the REMA data. Figure 2 was drawn by Ganzaa: park, forest and wetland outlines © OpenStreetMap contributors (ODbL); district boundaries from geoBoundaries, CC BY 4.0; countries and Lake Kivu from Natural Earth, public domain.

Photos: Cyamudongo forest, Wood Wildlife Photography, CC BY-SA 4.0; Ibanda-Makera, a natural forest connected to River Akagera, Ntirenganya D, CC BY-SA 4.0; via Wikimedia Commons.

Video: "Rwanda Education Board, S 4, Geography, Unit 7, Lesson: Vegetation in Rwanda", REB elearning, embedded from YouTube. The rest of the lesson, the worked examples and the exercises were written by Ganzaa.

This lesson adapts CC BY-SA material and is shared under CC BY-SA 4.0.

1More than half of the "forest" was planted

2The natural vegetation types

3Planted vegetation

4Where the natural forests survive

More than half of the "forest" was planted

The natural vegetation types

Planted vegetation

Where the natural forests survive